Fix Unix ARM floating point registers unwinding (#58915) (#358)

Fix Unix ARM floating point registers unwinding (#58915) (#358)

* Fix Unix ARM floating point registers unwinding

There are two problems unwinding ARM floating point registers. One is that the PAL_VirtualUnwind
is not supporting that and the second is that the libunwind we carry and use actually doesn't
have support for unwinding those.

This change updates the libunwind so that both exidx and dwarf ways of unwinding can unwind
these registers and also adds support to our PAL_VirtualUnwind to copy the callee saved
floating point registers D8..D15 between the native and windows style contexts.

I am planning to make a PR for the libunwind upstream, but given the very low amount of time
we have remaining for .NET 6 completion, I am making the change here first. Once I get them
upstream later, I'll update the whole libunwind from there.

* Enable the related test

Co-authored-by: Jan Vorlicek <jan.vorlicek@volny.cz>