[Generic-P4Orch] Add infra of supporting unique label to be used for SAI label attribute.

[ksravani-hcl]

Description
The main purpose of this helper class(NameLabelMapper) is to create and manage unique labels for SAI objects.
A unique label is a unique string identifier for a SAI object. It is used in warm boot for syncd reconciliation.
A SAI object will need a unique label if the existing SAI attrs cannot distinguish the object from each other.

The high level flow is the following:

1. Generate a unique label and pass it to the SAI attr when the SAI object is created. For new object, a new label will be generated and added into the NameLabelMapper. For existing object, the saved label will be return from NameLabelMapper.
2. During warmboot shut down, save the NameLabelMapper into STATE_DB. This STATE_DB table will persist across warm boot. This change will be part of the warm boot upstreaming. (Not in the current PR yet). Notice that label is a SAI attr, and hence it is in ASIC_DB as well, which will persist across warm boot.
3. During warmboot start up, read the STATE_DB and populate the NameLabelMapper.
4. During init_view, p4orch will process the requests in APPL_DB. Since NameLabelMapper is already populated, all objects that require labels will use the same labels as before warm boot. Syncd can uniquly identify each SAI object as the label will match in ASIC_DB.

What I did
Adding infra of supporting unique label to be used for SAI label attribute.
Implemented the Namelabelmapper utility to map SAI object keys to unique, timestamp-based labels. Integrated this into the Orchdaemon lifecycle, enabling the serialization of these mappings to STATE_DB using the schema SAI_OBJECT_TYPE|KEY to ensure persistent identification.

Why I did it
To provide a reliable mechanism to uniquely identify hardware objects during warm boot reconciliation. This prevents resource duplication and enables orchagent to correctly correlate existing hardware state with control plane requests for hitless upgrades.

How I verified it
Validated the logic with new C++ unit tests covering label allocation and collision prevention. Confirmed the end-to-end persistence flow via successful execution of the SWSS test suite.

Details if related

[mssonicbld]

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[yunang-c]

LGTM. @mint570 can you also take a look?

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[mssonicbld]

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[divyagayathri-hcl]

@prsunny can you take a look at this PR to see how this can impact upstream SONiC?

[kishanps]

@prsunny Can you please review this PR?
cc: @mint570

[mssonicbld]

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[ksravani-hcl]

@prsunny, can you please review this PR.

[prsunny]

@ksravani-hcl , the namelabel mapper can be a PR by itself and can be used by community.
Would you seperate the PR for namelabel mapper, create a doc https://github.com/sonic-net/SONiC on the usage and purpose so that community can use it for future.

[prsunny]

@mint570 for viz

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[prsunny]

@ksravani-hcl , the namelabel mapper can be a PR by itself and can be used by community. Would you seperate the PR for namelabel mapper, create a doc https://github.com/sonic-net/SONiC on the usage and purpose so that community can use it for future.

@ksravani-hcl , thanks for splitting the PR to have namelabel mapper. Please create the doc for usage examples and schematics

[ksravani-hcl]

@ksravani-hcl , the namelabel mapper can be a PR by itself and can be used by community. Would you seperate the PR for namelabel mapper, create a doc https://github.com/sonic-net/SONiC on the usage and purpose so that community can use it for future.

@ksravani-hcl , thanks for splitting the PR to have namelabel mapper. Please create the doc for usage examples and schematics

@prsunny, As you suggested, the NameLabelMapper usage document is prepared and raised as a document PR sonic-net/SONiC#2383, and we have updated the description of this PR with more details, can you please review and approve these PRs.
Thank you!