http2: fix compat stream read handling, add tests

Handle edge case where stream pause is called between resume being
called and actually evaluated. Other minor adjustments to avoid
various edge cases around stream events. Add new tests that cover
all changes.

Fixes: https://github.com/nodejs/node/issues/15491
PR-URL: https://github.com/nodejs/node/pull/15503


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>