Improve CPAN compiler and tooling compatibility

[fglock]

Summary

• add reusable compiler/runtime support for modern feature bundles, fatal warning pragmas, runtime glob redefinition warnings, compile-time call parsers, and special-block hooks
• use commonmark-java for the Markdown rendering surface instead of maintaining a custom parser; retain the small indexed trigram implementation because Commons Text does not provide the required index/Dice-scoring contract
• add Java compatibility backends used by Chandra and fix XML::LibXML element child-node compatibility

Validation

• make — pass
• ./jcpan -t Constructor::Sugar — 7 files, 95 tests pass
• ./jcpan -t Chandra::Markdown — 5 files, 83 tests pass
• ./jcpan -t XML::Writer::Simple — 7 files, 33 tests pass
• ./jcpan -t ISO::639 — 16 tests pass
• ./jcpan -t Search::Trigram — 10 files, 94 tests pass
• new unit tests were first validated with system Perl

Scope notes

• Test::Perl::Dist is excluded because its distribution also fails under system Perl (duplicate planning through LWP::Online and platform-specific Win32 assumptions).
• Games::Axmud is excluded because its native Gtk3/GObject dependency chain fails under system Perl on this host.
• The Java Object::Proto and Markdown::Simple implementations cover the API exercised by Chandra. Their distributions contain additional advanced/native APIs that are not claimed as complete here.
• make test-bundled-modules still reports the existing test-resource/current-directory failures (mostly missing t/*.inc helper resources); the primary full make build is green.