fix: various custom operator conformance fixes

[leakonvalinka]

• support V prefix in semver
• return null on errors in semver, ends_with, and fractional (already existed on starts_with)
• fix fractional fallback when total weight is zero

Fixes: #1942

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Related:

• fix: various custom operator conformance fixes java-sdk-contrib#1778
• fix: various custom operator conformance fixes js-sdk-contrib#1519
• fix: various custom operator conformance fixes dotnet-sdk-contrib#635
• fix: various custom operator conformance fixes python-sdk-contrib#386

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[gemini-code-assist]

Code Review

This pull request fixes an indentation issue in fractional.go and updates the semantic version parsing logic in semver.go to normalize uppercase 'V' prefixes. Additionally, a test case was added to semver_test.go to verify this normalization. I have no feedback to provide.

[toddbaert]

@leakonvalinka Thanks!

Looks great. I made some small tweaks for consistency with other implementations with this commit:

• used a JSON "round trip" to make the $ref replace much easier (because whitespace will be predictable)
• renamed a func (parseSemanticVersion to normalizeVersion)

I also updated the go-flagd-provider in use, which means we could update some of the excludes here (for instance, we were still using fractional-v1). I also added a comment here explaining why a lot of the exclusions are permanent and justified.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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