Fix ordering and hashing of version suffixes in Gitlab::VersionInfo

What does this MR do and why?

Fixes two suffix-handling defects in Gitlab::VersionInfo:

• Mixed string/integer suffix parts now sort deterministically instead of returning nil and causing sort or max to raise. Words sort before numbers, matching Gem::Version; previously defined ordering is unchanged.
• Versions with equivalent parsed suffixes, such as 1.0.1-rc1 and 1.0.1-rc01, now have matching hashes, fixing Hash lookups and uniq.

Cached version objects remain readable across upgrades and rollbacks. Rolling back restores the old comparison and hashing behavior.

Found while maintaining gitlab-mcp-server.

References

Closes #635968 (closed)

Screenshots or screen recordings

Not applicable: no UI change.

How to set up and validate locally

1. Open the Rails console on this branch with bundle exec rails console.

2. Verify mixed suffix ordering and equivalent-version deduplication:

   rc = Gitlab::VersionInfo.parse('16.0.0-rc1', parse_suffix: true)
   numbered = Gitlab::VersionInfo.parse('16.0.0-1', parse_suffix: true)
   [numbered, rc].sort.map(&:to_s)
   # => ["16.0.0-rc1", "16.0.0-1"]
   
   equivalent = Gitlab::VersionInfo.parse('16.0.0-rc01', parse_suffix: true)
   [rc.eql?(equivalent), rc.hash == equivalent.hash, [rc, equivalent].uniq.size]
   # => [true, true, 1]
   { rc => :found }[equivalent]
   # => :found

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