http2: fix graceful session close

[lundibundi]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

This is tied to
started with #20630, then #19852 and #20772.

The description is in the commits. This should fix our ECONNRESET during graceful close bugs in http2 tests.

Basically now we use socket.end() upon graceful close.

Also, I understand that now there is no way to actually destroy the socket if needed. If the second commit is accepted I planned to 'overload' session.destroy() to actually destroy the socket if we already initiated graceful close but want to destroy the session without waiting for FIN.

/cc @addaleax @jasnell @apapirovski @nodejs/http2