Add optional variant to requirement_level

[MadVikingGod]

This enables weaver to parse semantic convention v1.18.0

This will enable parsing of semantic conventions v1.13.0 - v1.18.0

I was looking to put a test in crates/weaver_resolver/data, but I don't know if that's appropriate. And, I don't fully grok the format of what I should put there to make sure that it is parsing appropriately.

I also don't know how to signify that this is a deprecated option and shouldn't be used in general cases.

Expands the supported versions found in #181

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 74.3%. Comparing base (9ab536f) to head (96e9766).

❗ Current head 96e9766 differs from pull request most recent head 78ad26b

Please upload reports for the commit 78ad26b to get more accurate results.

Files	Patch %	Lines
crates/weaver_semconv_gen/src/gen.rs	0.0%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #199     +/-   ##
=======================================
- Coverage   74.4%   74.3%   -0.1%     
=======================================
  Files         44      44             
  Lines       2918    2921      +3     
=======================================
  Hits        2172    2172             
- Misses       746     749      +3     

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[lquerel]

LGTM

[lquerel]

I also don't know how to signify that this is a deprecated option and shouldn't be used in general cases.

@MadVikingGod Ideally, I think we should generate a violation via the policy engine when the semconv registry is greater than or equal to v1.19.0. However, the version number is not in the YAML docs themselves but in the form of a tag. So, we'll need to find a way to expose it to the policies one way or another. We should create a GH issue for that.

[lquerel]

Added the policy into this list -> #185 (comment)