fix(jcpan URI::Find): silence spurious eunicefix and Wide-character warnings

[fglock]

Summary

jcpan -t URI::Find succeeds (619 tests pass) but emits two spurious warnings during build and test. This PR removes both.

1. Use of uninitialized value in join or string at Module/Build/Base.pm line 301

Module::Build's fix_shebang_line ends with:

$self->do_system($c->get('eunicefix'), $file) if $c->get('eunicefix') ne ':';

On real Perl $Config{eunicefix} is ':' (no-op), so the call is skipped. PerlOnJava's %Config was missing the key, so the guard evaluated undef ne ':' (true) and do_system(undef, $file) was invoked — log_verbose("@cmd\n") then interpolated undef.

Fix: add eunicefix => ':' to src/main/perl/lib/Config.pm.

(Side note: PerlOnJava attributed the warning to line 301 of Base.pm, which was misleading — the actual interpolation is in do_system/log_verbose. That's a pre-existing line-attribution issue, not addressed here.)

2. Wide character in print at Test2/Formatter/TAP.pm line 125 (×5)

t/Find.t prints non-ASCII URLs (Arabic, Russian, Chinese). Two combined causes:

• open.pm was a no-op stub, so use open ':std', ':encoding(utf8)' didn't actually apply layers to STDIN/STDOUT/STDERR.
• Even with explicit binmode, duplicateFileHandle (used by open $fh, '>&FILENO', which Test2::Util::clone_io invokes) replaced the original's LayeredIOHandle with a bare DupIOHandle, dropping the layers. PerlIO::get_layers(\*STDOUT) then reported an empty list, and clone_io produced a cloned handle without an :encoding/:utf8 layer, which then warned on every wide-character print.

Fixes:

• open.pm: parse :std + layer specs and apply via binmode to STDIN/STDOUT/STDERR.
• IOOperator.duplicateFileHandle: when the source is a LayeredIOHandle, dup the inner delegate and re-wrap each side in its own LayeredIOHandle carrying the same active layers.

Test plan

• jcpan -t URI::Find is clean (All tests successful. Result: PASS, no warnings, 619 tests).
• make (full unit-test suite) passes.

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