feat: add a new implementation of schema with ttl

[shekhar-rudder]

Description

This PR introduces schema invalidation based on a configurable TTL. When a schema entry expires, it is refreshed from the warehouse and updated in storage.

Changes:

• Added an expires_at column to the wh_schemas table.
• Implemented a new schema version (schema_v2), gated by a feature flag.
• In schema_v2:
  1. Entries in the table are marked with an expiration timestamp (now + TTL) upon insert/update.
  2. Reads first validate the schema’s expiration status—if valid, it is returned; otherwise, it is re-fetched from the warehouse.
• Updated database read/write methods to handle the new column.
• Modified the NewSchema function to accept whManager, allowing schema_v2 to reference the repository.
• Adjusted method signatures in the Handler interface to accept a context and return an error, as most schema_v2 methods now interact with the database.
• Extracted removeDeprecatedColumns and tableSchemaDiff from schemaV1 for reuse in schemaV2.

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Attention: Patch coverage is 71.58470% with 52 lines in your changes missing coverage. Please review.

Project coverage is 74.85%. Comparing base (66139a2) to head (f36f3e3).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
warehouse/schema/schema_v2.go	71.65%	25 Missing and 11 partials ⚠️
warehouse/router/state_export_data.go	23.80%	11 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5462      +/-   ##
==========================================
+ Coverage   74.79%   74.85%   +0.06%     
==========================================
  Files         440      441       +1     
  Lines       61490    61662     +172     
==========================================
+ Hits        45991    46157     +166     
+ Misses      12962    12957       -5     
- Partials     2537     2548      +11     

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