feat(gen): support custom time format

[abemedia]

This PR adds support for a new extension x-ogen-time-format which sets a format for encoding and decoding time values.
Also fixes some indentation on templates (mix of tabs and spaces).

Since I'm not that familiar with the codebase, let me know if I should do some things differently.

Closes #1063

[codecov]

Codecov Report

Attention: Patch coverage is 87.75510% with 6 lines in your changes missing coverage. Please review.

Project coverage is 71.44%. Comparing base (ce47f75) to head (dbd90b0).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
json/time.go	92.30%	1 Missing and 2 partials ⚠️
jsonschema/parser.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1334      +/-   ##
==========================================
- Coverage   71.45%   71.44%   -0.01%     
==========================================
  Files         190      190              
  Lines       15584    15587       +3     
==========================================
+ Hits        11135    11136       +1     
  Misses       3898     3898              
- Partials      551      553       +2     

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[tdakkota]

Thank you for your contribution!

Please move generated code changes to a separate commit.

Also, it would be nice to have a encode-decode-encode test for this feature, like one of these.

Everything else LGTM.

[abemedia]

@tdakkota Weirdly when testing on my Intel MacBook I can reproduce similar results as you on the benchmarks. On my M1 Format was actually faster (however the function you wrote in your comments beat it by a little).

Since we're leaving the json package functions I had removed, I changed TimeFormat to only return custom formats so the output of the template no longer changes if no custom format was set.

Also, I had forgotten to add support for parameters so I added that too.

Let me know if there's anything else.