Sync query link creation with record identity API (#119)

[atimin]

Closes #119

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• CHANGELOG.md has been updated (for bug fixes / features / docs)

What kind of change does this PR introduce?

Bug fix.

What was changed?

• Added record identity selector support to IBucket::QueryLinkOptions with record_entry and record_timestamp.
• Updated query link request serialization to send record_entry + record_timestamp and omit legacy index when identity is used.
• Added selector normalization/validation in CreateQueryLink:
  • default record_entry from a single explicit entry when only record_timestamp is provided,
  • require both identity fields together,
  • require identity selector for ReductStore API v1.19+,
  • keep legacy index behavior for older API versions.
• Updated query-link tests for API-aware behavior and added v1.19 record-identity coverage.

Related issues

• Sync query link creation with reduct-js#167 (record identity API) #119
• Fix query link creation for new record identity API reduct-js#167
• Query link can resolve to a different record than batch V2 query ordering reductstore#1332

Does this PR introduce a breaking change?

For ReductStore API v1.19+, links must be created using record_entry + record_timestamp instead of numeric-only index selector.

Other information:

• Local compile check passed (cmake -S . -B build-user -DREDUCT_CPP_USE_FETCHCONTENT=ON -DREDUCT_CPP_ENABLE_TESTS=ON and cmake --build build-user --target reduct-tests).
• Runtime integration tests were not run in this environment because no server was available at http://127.0.0.1:8383.