feat: Add Identify hooks to Client SDK

[abelonogov-ld]

Requirements

Adds BeforeIdentify / AfterIdentify hook stages to the existing hooks infrastructure, mirroring the evaluation series pattern. Hooks execute in forward order for BeforeIdentify and reverse (LIFO) order for AfterIdentify.
Wraps LdClient.IdentifyAsync with the identify hook series so that configured hooks receive callbacks before and after each identify operation, with IdentifySeriesResult.Completed on success and IdentifySeriesResult.Error on failure.
Threads maxWaitTime from Identify / IdentifyAsync into IdentifySeriesContext.Timeout so hooks have visibility into the caller's timeout configuration.

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

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Note

Medium Risk
Changes LdClient initialization and Identify/IdentifyAsync flow to run new hook callbacks and to always emit an identify series result, which could affect timing/ordering and error propagation around context changes.

Overview
Adds an identify hook series to the SDK hook infrastructure, introducing Hook.BeforeIdentify/Hook.AfterIdentify plus new IdentifySeriesContext (includes timeout) and IdentifySeriesResult (Completed/Error).

Extends the internal hook executor (IHookExecutor, Executor, NoopExecutor) with an async IdentifySeries pipeline that runs hooks in forward order before identify and reverse order after, logging and isolating hook-stage failures while still propagating identify exceptions.

Updates LdClient to route both startup identify event recording and Identify/IdentifyAsync through the new identify series (including threading maxWaitTime into hook context) and adds unit tests covering ordering, data passing, logging on hook errors, result status, and activation during init.

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