Reduce default number of bits used per RSA certificate key to 2048

[eduser25]

Trading off bits on RSA key size for performance.

Shows a 12x to 15x less time spent generating certificates, which right
now is synchronous inside webhook handling.

see #1931 for additional context
fixes #1931

Affected area:

• Control Plane [X]
• Certificate Management [X]
• Security [X]
• Performance [X]

Please answer the following questions with yes/no.

• Does this change contain code from or inspired by another project? If so, did you notify the maintainers and provide attribution?
  No

[codecov-io]

Codecov Report

Merging #1940 into main will decrease coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1940      +/-   ##
==========================================
- Coverage   58.50%   58.30%   -0.20%     
==========================================
  Files         131      131              
  Lines        5270     5272       +2     
==========================================
- Hits         3083     3074       -9     
- Misses       2184     2195      +11     
  Partials        3        3              

Impacted Files	Coverage Δ
...ertificate/providers/tresor/certificate_manager.go	64.04% <0.00%> (-12.36%)	⬇️
pkg/catalog/routes.go	77.77% <0.00%> (ø)
pkg/catalog/mock_catalog.go	0.00% <0.00%> (ø)
pkg/kubernetes/util.go	95.00% <0.00%> (+0.55%)	⬆️

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