GH-1357: parse Flight SQL JDBC boolean properties case-insensitively - #1358

What's Changed

ArrowFlightConnectionProperty.getBoolean only treated 1 and the exact lowercase true as true, and connection-string values are not normalized, so useEncryption=TRUE (or True) parsed as false. Since useEncryption defaults to true and drives withEncryption, that silently downgraded the connection to plaintext and sent the auth handshake and credentials in the clear. This compares true case-insensitively while still honoring 1, matching how JDBC drivers normally parse boolean options.

Closes #1357.