SNOW-961482 Change OCSP response cache key to base64 encoded certID

[sfc-gh-dheyman]

Description

Please explain the changes you made here.

Checklist

• Code compiles correctly
• Run make fmt to fix inconsistent formats
• Run make lint to get lint errors and fix all of them
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (25d3956) 82.79% compared to head (4b53e47) 82.78%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
ocsp.go	82.60%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #969      +/-   ##
==========================================
- Coverage   82.79%   82.78%   -0.01%     
==========================================
  Files          50       50              
  Lines        9625     9633       +8     
==========================================
+ Hits         7969     7975       +6     
- Misses       1656     1658       +2     

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