feat(mappers): Stream name can now be accessed in stream maps

[holly-evans]

Description

Allow users to reference the stream name or alias in stream maps under a special key, similar to record and config:

{
    "stream_maps": {
        "*": {
            "source_table": "__stream_name__",
            "source_data": "record",
        }
    }
}

Add two tests for existing functionality of self and _ keys

Related Issues

• Closes feat: Support using the stream name or alias in the context of a stream map #2283

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📚 Documentation preview 📚: https://meltano-sdk--2699.org.readthedocs.build/en/2699/

[codspeed-hq]

CodSpeed Performance Report

Merging #2699 will not alter performance

_{Comparing holly-evans:issue-2283-use-stream-name-in-stream-map-context (2a46ecc) with main (9bf104e)}

Summary

✅ 6 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.50%. Comparing base (9bf104e) to head (2a46ecc).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2699   +/-   ##
=======================================
  Coverage   90.50%   90.50%           
=======================================
  Files          62       62           
  Lines        4994     4994           
  Branches      974      974           
=======================================
  Hits         4520     4520           
  Misses        328      328           
  Partials      146      146           

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