Add DBD::mysql compatibility shim backed by JDBC

[fglock]

Summary

Add a PerlOnJava DBD::mysql compatibility shim backed by the existing
DBD::JDBC infrastructure and MySQL Connector/J.

Motivation

PerlOnJava already provides DBI through JDBC and has a working DBD::JDBC
base driver plus a DBD::SQLite DSN-translation shim. However, CPAN modules
that use the conventional dbi:mysql: DSN or declare DBD::mysql currently
cannot load or connect.

MetaCPAN lists dozens of reverse dependents, including:

• Mojo::mysql
• PApp
• DBIx::Class::Storage::DBI::mysql::Retryable
• Tapper::Schema
• DBIx::TxnPool
• Mojolicious::Command::migration
• Wiki::Toolkit
• Coro::Mysql
• DBIx::MysqlCoroAnyEvent
• DBIx::SecureCGI
• MySQL::Util
• App::Prove::Plugin::MySQLPool

The current CPAN failure that prompted this request is
MySQL::TableInfo-1.01, whose pure-Perl implementation depends on
DBD::mysql and a live MySQL database.

Reverse-dependency evidence:
https://metacpan.org/dist/DBD-mysql/requires

Proposed scope

• Add src/main/perl/lib/DBD/mysql.pm as a PerlOnJava compatibility driver.
• Inherit the common handle implementation from DBD::JDBC.
• Translate common DSNs such as:
  • dbi:mysql:database=name
  • dbi:mysql:database=name;host=host;port=3306
  • dbi:mysql:name;mysql_socket=/path/to/socket
    into Connector/J URLs.
• Preserve standard DBI operations: connect, prepare, execute, fetch,
  transactions, metadata, quoting, and error handling.
• Provide common MySQL compatibility fields such as mysql_insertid where
  JDBC exposes an equivalent.
• Keep Connector/J optional and use the existing Configure.pl/classpath
  driver configuration path.
• Add focused DSN and handle tests without requiring a live server, plus an
  optional integration suite against MySQL/MariaDB when a JDBC driver and
  server are available.

Compatibility boundaries

This should not perform broad SQL rewriting. MySQL SQL semantics should be
provided by MySQL/MariaDB through Connector/J. MySQL-specific attributes and
methods such as mysql_auto_reconnect, mysql_enable_utf8, and
mysql_server_prepare need explicit mapping, documented no-op behavior, or a
clear unsupported-feature error.

The shim must not claim to replace the native driver for code that depends on
native client-library behavior or undocumented DBD::mysql internals.

Acceptance criteria

• use DBD::mysql succeeds under PerlOnJava without XS loading.
• Standard DBI->connect('dbi:mysql:...', ...) reaches Connector/J.
• A MySQL-backed smoke test exercises schema introspection, prepared
  statements, transactions, generated IDs, and error propagation.
• MySQL::TableInfo can run its upstream test when supplied with a MySQL
  server and Connector/J.
• JVM and interpreter backends have equivalent behavior for the shim.