Support multi-packet sysex messages in JvmMidiAccess

[AlecJY]

Multi-packet sysex messages are useful for controlling transmission speed. Additionally, JVM sometimes splits sysex messages into multiple packets.

As JavaDoc mentioned, the first sysex message starts with 0xF0 as usual, and additional sysex messages start with 0xF7. For example, if we want to split the following message into three packets:

0xF0 0x7D 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0xF7

It would be something like this:

0xF0 0x7D 0x01 0x02
0xF7 0x03 0x04
0xF7 0x05 0x06 0xF7

This patch removes the leading 0xF7 when receive a sysex staring with 0xF7, and adds a 0xF7 before sending the sysex message if the message is an additional sysex message.

This patch might not functional correctly when sending multi-packet sysex messages on most JVM due to some bugs. The bugs are fixed in openjdk/jdk#16477 and openjdk/jdk#16399. Currently, the patch is confirmed to work with OpenJDK 22-ea+25 and above. Compatibilities with older versions are expected after the completion of backporting.

[atsushieno]

Thanks, that's very helpful to whoever wants solid sysex support (who doesn't) !