in_docker: Implement a capability for cgroups V2

[cosmo0920]

Currently, in_docker does not provide cgroups v2.
In this PR, I added a capability to handle cgroups v2 metrics for Docker.

This is related for #5949.

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Enter [N/A] in the box, if an item is not applicable to your change.

Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change

$  sudo bin/fluent-bit -i docker -o stdout 

• Debug log output from testing the change

In other terminals:

$ docker run -it --rm ubuntu:jammy bash

$ docker run -it --memory 300MB --rm debian:bullseye bash

fluent-bit log:

Fluent Bit v2.2.0
* Copyright (C) 2015-2023 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/10/26 15:18:53] [ info] Configuration:
[2023/10/26 15:18:53] [ info]  flush time     | 1.000000 seconds
[2023/10/26 15:18:53] [ info]  grace          | 5 seconds
[2023/10/26 15:18:53] [ info]  daemon         | 0
[2023/10/26 15:18:53] [ info] ___________
[2023/10/26 15:18:53] [ info]  inputs:
[2023/10/26 15:18:53] [ info]      docker
[2023/10/26 15:18:53] [ info] ___________
[2023/10/26 15:18:53] [ info]  filters:
[2023/10/26 15:18:53] [ info] ___________
[2023/10/26 15:18:53] [ info]  outputs:
[2023/10/26 15:18:53] [ info]      stdout.0
[2023/10/26 15:18:53] [ info] ___________
[2023/10/26 15:18:53] [ info]  collectors:
[2023/10/26 15:18:53] [ info] [fluent bit] version=2.2.0, commit=4acd344399, pid=335975
[2023/10/26 15:18:53] [debug] [engine] coroutine stack size: 24576 bytes (24.0K)
[2023/10/26 15:18:53] [ info] [storage] ver=1.5.1, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/10/26 15:18:53] [ info] [cmetrics] version=0.6.4
[2023/10/26 15:18:53] [ info] [ctraces ] version=0.3.1
[2023/10/26 15:18:53] [ info] [input:docker:docker.0] initializing
[2023/10/26 15:18:53] [ info] [input:docker:docker.0] storage_strategy='memory' (memory only)
[2023/10/26 15:18:53] [debug] [docker:docker.0] created event channels: read=21 write=22
[2023/10/26 15:18:53] [ info] [input:docker:docker.0] Detected cgroups v2
[2023/10/26 15:18:53] [debug] [stdout:stdout.0] created event channels: read=23 write=24
[2023/10/26 15:18:53] [ info] [sp] stream processor started
[2023/10/26 15:18:53] [ info] [output:stdout:stdout.0] worker #0 started
[2023/10/26 15:18:54] [debug] [input chunk] update output instances with new chunk size diff=109, records=1, input=docker.0
[2023/10/26 15:18:54] [debug] [input chunk] update output instances with new chunk size diff=112, records=1, input=docker.0
[2023/10/26 15:18:55] [debug] [task] created task=0x7f13e801ece0 id=0 OK
[2023/10/26 15:18:55] [debug] [output:stdout:stdout.0] task_id=0 assigned to thread #0
[0] docker.0: [[1698301134.146797664, {}], {"id"=>"1a38a7677732", "name"=>"confident_snyder", "cpu_used"=>22631, "mem_used"=>823296, "mem_limit"=>314572800}]
[1] docker.0: [[1698301134.147009000, {}], {"id"=>"043b521509b6", "name"=>"objective_bassi", "cpu_used"=>53562, "mem_used"=>1208320, "mem_limit"=>18446744073709551615}]
[2023/10/26 15:18:55] [debug] [out flush] cb_destroy coro_id=0
[2023/10/26 15:18:55] [debug] [input chunk] update output instances with new chunk size diff=109, records=1, input=docker.0
[2023/10/26 15:18:55] [debug] [input chunk] update output instances with new chunk size diff=112, records=1, input=docker.0
[2023/10/26 15:18:55] [debug] [task] destroy task=0x7f13e801ece0 (task_id=0)
^C[2023/10/26 15:18:55] [engine] caught signal (SIGINT)
[2023/10/26 15:18:55] [debug] [task] created task=0x7f13e801f3e0 id=0 OK
[2023/10/26 15:18:55] [debug] [output:stdout:stdout.0] task_id=0 assigned to thread #0
[2023/10/26 15:18:55] [ warn] [engine] service will shutdown in max 5 seconds
[2023/10/26 15:18:55] [ info] [input] pausing docker.0
[0] docker.0: [[1698301135.146551719, {}], {"id"=>"1a38a7677732", "name"=>"confident_snyder", "cpu_used"=>22631, "mem_used"=>823296, "mem_limit"=>314572800}]
[1] docker.0: [[1698301135.146633514, {}], {"id"=>"043b521509b6", "name"=>"objective_bassi", "cpu_used"=>53562, "mem_used"=>1208320, "mem_limit"=>18446744073709551615}]
[2023/10/26 15:18:55] [debug] [out flush] cb_destroy coro_id=1
[2023/10/26 15:18:55] [debug] [task] destroy task=0x7f13e801f3e0 (task_id=0)
[2023/10/26 15:18:56] [ info] [engine] service has stopped (0 pending tasks)
[2023/10/26 15:18:56] [ info] [input] pausing docker.0
[2023/10/26 15:18:56] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2023/10/26 15:18:56] [ info] [output:stdout:stdout.0] thread worker #0 stopped

• Attached Valgrind output that shows no leaks or memory corruption was found

==339923== 
==339923== HEAP SUMMARY:
==339923==     in use at exit: 0 bytes in 0 blocks
==339923==   total heap usage: 2,933 allocs, 2,933 frees, 838,012 bytes allocated
==339923== 
==339923== All heap blocks were freed -- no leaks are possible
==339923== 
==339923== For lists of detected and suppressed errors, rerun with: -s
==339923== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[edsiper]

@cosmo0920 thank you, let's add unit tests in a different PR, you can use a hard copy of sysfs/procfs and custom paths to them to test in a runtime environment