Add Schema Registry to Provide Table Metadata

[suddendust]

Description

This PR introduces a way to get table schema information using the SchemaRegistry interface. This interface provides methods to retrieve a table's metadata from the underlying DB. For PG, this is the query that is used:

postgres=# SELECT "column_name", "udt_name", "is_nullable" FROM information_schema.columns WHERE table_schema = 'public' AND "table_name" = 'myTestFlat';
 column_name  |  udt_name   | is_nullable 
--------------+-------------+-------------
 _id          | int4        | NO
 item         | text        | YES
 price        | int4        | YES
 quantity     | int4        | YES
 date         | timestamptz | YES
 in_stock     | bool        | YES
 tags         | _text       | YES
 categoryTags | _text       | YES
 props        | jsonb       | YES
 sales        | jsonb       | YES
 numbers      | _int4       | YES
 scores       | _float8     | YES
 flags        | _bool       | YES

Cache Refresh and Expiry

This registry fetches and caches column metadata from PostgreSQL's information_schema on demand. It provides:

1. Lazy loading: Schema metadata is fetched only when first requested for the particular table.
2. TTL-based caching: Cached schemas expire after a configurable duration (default: 24 hours).
3. Circuit breaker: Prevents excessive database calls by enforcing a cooldown period between refresh attempts for missing columns (default: 15 minutes).

Testing

[x] Added UTs.
[x] Added integration tests.

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

❌ Patch coverage is 94.62366% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.47%. Comparing base (e434dfa) to head (602037b).

Files with missing lines	Patch %	Lines
...documentstore/postgres/PostgresSchemaRegistry.java	84.00%	3 Missing and 1 partial ⚠️
...a/org/hypertrace/core/documentstore/Datastore.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #263      +/-   ##
============================================
+ Coverage     80.26%   80.47%   +0.21%     
- Complexity     1337     1380      +43     
============================================
  Files           231      234       +3     
  Lines          6080     6171      +91     
  Branches        545      551       +6     
============================================
+ Hits           4880     4966      +86     
- Misses          826      830       +4     
- Partials        374      375       +1     

Flag	Coverage Δ
integration	80.47% <94.62%> (+0.21%)	⬆️
unit	58.54% <93.54%> (+0.52%)	⬆️

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