Mount files db in RAM

[splakhonin]

Based on the following documentation it's cool to add the possibility to map database files into RAM.
https://docs.gitlab.com/runner/executors/docker.html#mount-a-directory-in-ram

`[runners.docker]

For the main container

[runners.docker.tmpfs]
"/var/lib/mysql" = "rw,noexec"

For services

[runners.docker.services_tmpfs]
"/var/lib/mysql" = "rw,noexec"`

As docker/sdk generates a docker-compose.yml, here we have a volume or tmpfs mount definition, https://docs.docker.com/compose/compose-file/compose-file-v3/#long-syntax-3

The idea is to add a configuration to switch on/off mounting map database files into RAM.

[alexanderM91]

Subject: Update on Performance Testing with tmpfs Mounts

👋,

I’d like to provide a brief summary regarding the recent performance testing request.

We successfully executed the tests using tmpfs mounts.

Testing branch: test/in-mem-volume
Note: The volume type was modified for all services, not just the database.
Results:
Unfortunately, we did not observe any positive performance improvements. The CI execution time remained unchanged.

Additionally, there was no noticeable performance increase for local development either.

If I overlooked anything or if you'd like to review the results further, please feel free to let me know. I'm happy to provide additional details or assist with further checks! 😊

Additional Observations:
While tmpfs may provide performance benefits in some scenarios, I wasn’t anticipating significant improvements here, as approximately 95% of the execution time is consumed by application-specific processes (e.g., composer install, console command execution, etc.).

Looking forward to your thoughts!

Best regards,
Alex

cc: @zeetabit @splakhonin @fsmeier