Bump Mono version -> 3.8.0
[mcs] Update codegen for boolean loads. Fixes #21685
[jit] Avoid making generic calls from gsharedvt methods normally, go through the rgctx infrastructure instead. Fixes #21677.
[jit] Fix enum->int casts in gsharedvt code. Fixes #21893.
[runtime] Fix Process.PrivateMemorySize64 etc. on ios. Fixes #21882.
[System.Net.Http] Handle quoted filename value. Fixes #21960
Revert "[mcs] Use closed delegate over static generated methods from anonymous methods"

This reverts commit 7edcd42a15939cb356121dbbc8d05cdd8f035835.

Revert this as it causes blocker https://bugzilla.xamarin.com/show_bug.cgi?id=21651.
Revert "[mcs] Use closed delegate over static generated methods from anonymous methods"

This reverts commit 7edcd42a15939cb356121dbbc8d05cdd8f035835.

Conflicts:
	mcs/tests/ver-il-net_4_5.xml
[System] Use xamarin.com instead of mono-project.com for DNS tests

The latter is now hosted on a different IP behind a CDN and the IP may change depending on location.
Using xamarin.com instead fixes the tests for now.
[runtime] Fix the leaking of mach ports introduced by 98bbf8512aec0fa01b4426583280f6d231d22187. Fixes #22068.
Some fixes
merge from 3.8.0-yandex6