feat(regex): implement (*ACCEPT) in vendored Joni

[fglock]

Summary

• parse (*ACCEPT) as a native vendored-Joni control-verb AST node and opcode
• preserve Perl boundaries for top-level matches, subpattern calls, positive lookaheads, and runtime dynamic patterns
• close captures at the accepted endpoint and complete abandoned dynamic/backtracking continuations exactly once
• route ACCEPT-bearing patterns to Joni and bypass mandatory-suffix optimization when control flow can skip that suffix
• update the history-free Joni design and regex feature matrix

All new vendored-Joni sources retain the upstream MIT notice. Existing org.joni source namespaces remain unchanged; standalone packaging continues to relocate them to org.perlonjava.internal.joni.

Validation

• prove src/test/resources/unit/regex/accept_control_verb.t: 13/13 on standard Perl
• JVM backend: 13/13
• interpreter backend: 13/13
• imported Joni tests: pass, including dedicated ACCEPT cases
• make: pass, no warnings
• focused upstream direct/thread pair: 24/555 passing and 30/555 executed in each file, up from 22 passing and 28 executed before this slice; next blocker is optimistic callback conditions at line 138
• full perl dev/tools/perl_test_runner.pl perl5_t/t/re/: 80 files, 50,718 passing assertions, zero timeouts

Baseline comparison

Compared file-by-file with ../PerlOnJava/logs/test_20260815_080000_958.log:

• 26 regex files improved
• 53 retained the same passing count
• no files are missing or newly added
• regexp_unicode_prop.t is 1019/1110 versus the historical 1031/1110; a detached, clean origin/master build reproduces the same 1019/1110 result, so this is inherited from merged main and is not introduced by this branch

The ACCEPT-specific gain is visible in both pat_re_eval.t and pat_re_eval_thr.t, which move from the PR 970 postbase 22/555 to 24/555.

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