Add JRuby 10.0.5.0 and 10.1.0.0 to test matrix

[silug]

Short description

Adding JRuby 10 to the test matrix exposed RSpec failures:

• JRuby 10's backtrace format reports module methods unqualified ('stack' instead of 'Puppet::Pops::PuppetStack.stack'), so the PUPPET_STACK_INSERTION_FRAME regex never matched and PuppetStack pseudo-frames stopped being interleaved into log backtraces. Broaden the regex to handle Ruby 3.3 (backtick), Ruby 3.4+ (qualified) and JRuby 10+ (unqualified) formats.
• The integration specs for agent logging and the RDoc parser depend on the syslog and rdoc gems, which are restricted to platforms: [:ruby] in the Gemfile and so are absent on JRuby; skip those describes on JRuby, matching the existing idiom used elsewhere.
• JRuby 10.1.0.0 raises ArgumentError('string contains null byte') instead of MRI's 'path name contains null byte' when a filename contains a NUL; accept either message in the affected json/yaml specs.

Fix generated by Claude.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
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• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)