fix: jcpan -t Class::Trait PerlOnJava bugs + portable unit tests

[fglock]

Summary

Two related commits:

Commit 1 — Four PerlOnJava bugs exposed by jcpan -t Class::Trait

1. Parser: require File::Spec->catfile(...) was parsed as (require File::Spec)->catfile(...), dispatching the method on the bareword's require result (1) and producing Can't locate object method "catfile" via package "1". Now: when a require-bareword is followed by ->, restore the position and parse the whole thing as an expression (matches Perl semantics). Fixes 5 of 9 failing test files in Class::Trait.

2. bless after stash anonymisation: RuntimeStash.undefine() anonymised the existing blessId AND left it in the cache, so any subsequent bless({}, "Pkg") returned an object whose ref was __ANON__. The Class::Trait test suite hits this in clean_inc(). Now: drop the className→id cache entry on anonymise so fresh blesses allocate a new id mapped to the real class name. Also: undef *Pkg:: (RuntimeGlob.undefine on a ::-suffixed name) no longer anonymises at all — Perl semantics: only undef %Pkg:: anonymises.

3. RuntimeHash each() iterator: clearing or reassigning a hash (%h = (), undef %h, hash set from a list) did not reset the hashIterator. A subsequent each %h after re-populating threw ConcurrentModificationException. Class::Trait's apply() uses _clear_all_caches() and then re-iterates via each — under PerlOnJava the second call after a previous croak silently iterated zero entries, causing requirement checks to be skipped. Now: reset hashIterator in all three clear-points.

4. RuntimeGlob.undefine() leaked DESTROY for ARRAY/HASH slots: undef *Pkg::arr and undef *Pkg::hsh replaced the slot with a fresh empty container without calling .undefine() on the old one, so blessed values inside were orphaned without firing destructors. Now: call .undefine() on the old array / hash before replacing. Covered by unit/refcount/destroy_glob_undef.t (added in this commit, fails before this fix and passes after, also passes under system prove).

Result on ./jcpan -t Class::Trait

	Failed test files	Failed subtests
before	9 / 17	8 / 219
after	2 / 17	1 / 405

Remaining failures are unrelated: t/pod_coverage.t needs B::GV::GvFLAGS, t/070_Trait_mod_perl_test.t has one warning-leak subtest under prove.

Commit 2 — All unit tests now pass under system perl

Running prove -r src/test/resources/unit/ previously failed 14 of 210 test files (each relying on PerlOnJava-permissive behavior, a misuse of Perl idioms, or an XS dependency without a skip guard). All now pass under both ./jperl (via make) and system prove:

File(s)	Issue
statement.t	state $x = 0 unless defined $x — strict rejects (refers to $x before declaration). Rewrote to declare state $x then conditionally init.
interpreter_myhash_myarray_scope_exit.t	defined((my %copy=$h) ? $copy{k} : ...) — my %copy not visible inside same expression under strict. Hoisted declaration.
7× netssleay_*.t	XS Net::SSLeay not always installed; added Test::More::plan(skip_all) guard.
encoding_pragma.t	Tests our no-op encoding.pm stub; CPAN's dies on use encoding;. Detect system perl by absence of jar: in @inc and force-load our stub. Hoisted use Encode to top to avoid DynaLoader bootstrap failure under eval STRING.
source_filter_scope.t	Filter::Util::Call's filter_read doesn't operate on eval STRING (sees EOF immediately). Rewrote to write a real .pm to tempdir + require.
weaken.t, destroy.t	my @log; sub DESTROY { push @log, ... } triggers "Variable @log will not stay shared" — named subs in named packages don't bind to per-invocation my scope. Switched to @PkgName::log package globals. destroy.t also needed use warnings for (in cleanup) warnings to fire through $SIG{__WARN__}.
overload/constant.t	Used $^H{integer} = sub{} shortcut; switched to standard overload::constant integer => sub{} (PerlOnJava already supports it). Relaxed handler-args assertion (real Perl 5.42 passes undef as category arg vs PerlOnJava's "integer"). bigint smoke wrapped in SKIP guard.

Test plan

• make (full unit suite, jperl, 5 parallel shards) → BUILD SUCCESSFUL
• prove -r src/test/resources/unit/ (system perl) → 209/209 files, 7820/7820 tests PASS
• New unit/refcount/destroy_glob_undef.t fails before fix variable declaration in if expression causes bytecode inconsistency #4, passes after, also passes under system perl
• ./jcpan -t Class::Trait improved from 9 to 2 failing test files

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