feat(translator): extension server should fail close

[liorokman]

This PR changes the default behavior for extension servers to fail-close instead of fail open.

Which issue(s) this PR fixes:
Fixes #4155

Release Notes: Yes

[codecov]

Codecov Report

Attention: Patch coverage is 61.26126% with 43 lines in your changes missing coverage. Please review.

Project coverage is 66.35%. Comparing base (469de2f) to head (2357622).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/extension/registry/extension_manager.go	0.00%	16 Missing ⚠️
internal/xds/translator/translator.go	81.01%	10 Missing and 5 partials ⚠️
internal/xds/translator/extension.go	25.00%	8 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4936      +/-   ##
==========================================
+ Coverage   66.27%   66.35%   +0.08%     
==========================================
  Files         209      209              
  Lines       32035    32124      +89     
==========================================
+ Hits        21231    21316      +85     
- Misses       9541     9543       +2     
- Partials     1263     1265       +2     

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[liorokman]

/retest

[liorokman]

/retest