feat(config): add optional dimensions to text2vec-aws vectorizer

[g-despot]

Adds an optional dimensions parameter (output embedding dimensionality) to the text2vec-aws vectorizer config. Omitted when unset, so the server applies its default.

Closes #2071

[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 86.60%. Comparing base (95b5d76) to head (0e8620b).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2078      +/-   ##
==========================================
- Coverage   86.64%   86.60%   -0.04%     
==========================================
  Files         300      300              
  Lines       23172    23174       +2     
==========================================
- Hits        20077    20070       -7     
- Misses       3095     3104       +9     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.