Ensure full JRuby 10.0 and 10.1 support

[chadlwilson]

There are a few issues that are blocking some work on Warbler that need some assistance.

Tracking them here to move forward:

• "Full" JRuby 10.0 and Rails 8.0 support
  • Verify Warbler's own compatibility with JRuby 10.0
  • however when using with jruby-rack <= 1.2.6 will swallow start-up errors due to CompatVersion problems and needs Release jruby-rack 1.2.7 jruby-rack#430
  • Remove redundant notes from https://github.com/jruby/warbler#troubleshooting after jruby-rack release
• "Full" JRuby 10.1 support
  • Release jruby-rack 1.2.7 jruby-rack#430
  • fix: allow use with JRuby 10.1 / Bundler 4.0 jbundler#108
    • jbundler 0.9.x release
  • Recheck Warbler PR fix: ensure compatibility with JRuby 10.1 #623
  • Warbler 2.1.x release
• "Full" Rails 8.1 and Rack 3.x support
  • Rack 3.x / Rails 8.1 support jruby-rack#304
  • Release of jruby-rack 1.3.x
  • Warbler 2.1.1+ release with chore: relax jruby-rack requirement to allow compatibility with upcoming 1.3.x #593 included

Out-of-scope

• some specific handling/support required for activerecord-jdbc gems on Rails 8.0 and 8.1.