Support multiple database for DPU

[ganglyu]

Why I did it

We have updated database configuration to support multiple databases for smartswitch.
And then we need to update sonic-gnmi to support new database configuration and new GNMI path for smartswitch.
HLD PR: sonic-net/SONiC#1625

How I did it

• Support new database configuration

{
    "INCLUDES" : [
        {
            "include" : "../../redis/sonic-db/database_config.json"
        },
        {
            "container_name" : "dpu0",
            "include" : "../../redisdpu0/sonic-db/database_config.json"
        }
    ],
    "VERSION" : "1.0"
}

Use a single layer instance for each device to support multiple asic and multiple dpu.
For example, for multiple asic, the instances can be named localhost, asic0, asic1, and so on. For multiple dpu, the instances can be named localhost, dpu0, dpu1, and so on. For multiple asic npu and multiple dpu, the instances can be named localhost, asic0, asic1, ..., dpu0, dpu1, and so on.

        "DPU_APPL_DB" : {
            "id" : 15,
            "separator": ":",
            "instance" : "redis",
            "format": "proto"
        },

• Update GNMI path to support multiple database

I add a new element in GNMI path to support database instance.

/APPL_DB/dpu0/DASH_VNET_TABLE/vnet1/

The second element is used for target database instance, and it can be localhost, asic0, asic1, ..., dpu0, dpu1, and so on.

How to verify it

Run unit test for sonic-gnmi.
Run end to end test for dash and gnmi.

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[qiluo-msft]

localhost

This is more general design change, not directly related to multiple database. Let's use a separate PR. #Closed

[ganglyu]

Done

[qiluo-msft]

GetDbSeparatorByDBKey

Many functions below are 1:1 mapping of swsscommon functions. Why not directly using swsscommon functions? What is the value of the extra wrapper? #Closed

[ganglyu]

This wrapper can translate swsscommon exception to error and invoke swsscommon initialize API.