Port Crypt::Rijndael to PerlOnJava Java crypto backend

[fglock]

Summary

Port Crypt::Rijndael 1.16 to PerlOnJava.

Current failure

The distribution is XS-only (Rijndael.xs and _rijndael.c). Its Perl
module calls XSLoader::load, and PerlOnJava currently reports:

Can't load loadable object for module Crypt::Rijndael: no Java XS implementation available

All three upstream test files fail at load time, before any subtests run:
t/00_load.t, t/modes.t, and t/rt/27632.t.

Failure log:
/tmp/cpan_random_logs/20260824-171428-41866/failures/Crypt-Rijndael--from--Crypt-Rijndael.log

Why this is worth porting

Crypt::Rijndael has a substantial reverse-dependency footprint. MetaCPAN
lists users including Crypt::OpenPGP, Lemonldap::NG::Common, XAO::Web,
App::OATH, Crypt::OpenToken, Crypt::Fernet, HTTP::Cookies::Chrome,
DBIx::Squirrel, Data::Entropy, and Perlmazing. Local CPAN metadata also
shows dependencies from AC::Yenta and MooX::Role::CryptedPassword.

Proposed implementation

• Replace the XS-only loading path with a PerlOnJava implementation backed by
  Java's standard cryptography APIs where the semantics match.
• Preserve the public API and constants, including new, keysize,
  blocksize, set_iv, encrypt, and decrypt.
• Cover the modes exercised by the upstream suite: CBC, CFB, CTR, ECB, and
  OFB; verify PCBC behavior if it is part of the public compatibility surface.
• Support 128-, 192-, and 256-bit keys and the 16-byte block size.
• Add permanent bundled regression coverage using the upstream test vectors;
  validate both JVM and interpreter backends.
• Document any Rijndael variants that cannot be represented by the Java
  provider rather than silently accepting incompatible behavior.

This is a crypto portability port, so it should use the normal Java
cryptography infrastructure rather than an FFM/native-call shim.

References

• MetaCPAN reverse dependencies: https://metacpan.org/module/Crypt%3A%3ARijndael/requires
• App::OATH dependency metadata: https://metacpan.org/release/MBRADSHAW/App-OATH-1.20260324
• Data::Entropy dependency metadata: https://metacpan.org/release/RRWO/Data-Entropy-0.009