feat: add optional location parameter to text2vec-google vectorizer

[g-despot]

Adds an optional location parameter (Google Vertex AI region) to the text2vec-google vectorizer config. When unset it is omitted from the module config, so the server applies its default.

Closes #2070

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.64%. Comparing base (78fa5f7) to head (cec15ca).
⚠️ Report is 193 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2075      +/-   ##
==========================================
- Coverage   87.95%   86.64%   -1.31%     
==========================================
  Files         280      300      +20     
  Lines       21664    23173    +1509     
==========================================
+ Hits        19054    20079    +1025     
- Misses       2610     3094     +484     

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