Make copy_stack_data support configurable.

Make copy_stack_data support configurable.

By default when called through macros like MONO_ENTER_GC_UNSAFE
code will always dump current registers into stack space on hybrid/coop.
The registers will be scanned but only when hitting a GC and when running
in GC unsafe, that will only happen when we block in the enter or hit a safe
point at a later point in time. There are currently a couple of frequent
scenarios where we go into GC safe when thread won't be suspended and in
that case the copy of the registers will only reflect the state when
entering GC unsafe.

Commits add option to enable/disable copy_stack_data support in configure step:
--enable-copy-stack-data, --disable-copy-stack-data.

copy_stack_data is enabled by default on all platforms except desktop platforms
macos, linux and windows (both 32/64-bit), since these platforms already support
full context as well as capabilities to scan the stack of a running thread.