[x86/Linux] Fix regdisplay initialization in case of WIN64EXCEPTIONS (dotnet/coreclr...

[x86/Linux] Fix regdisplay initialization in case of WIN64EXCEPTIONS (dotnet/coreclr#14296)

Method Debugger::IsThreadAtSafePlaceWorker for x86 sets values only
for ControlPC and PCTAddr fields of REGDISPLAY but there is assert
in StackFrameIterator::Init that checks that field pCurrentContext
is not NULL if WIN64EXCEPTIONS is defined.

This patch uses FillRegDisplay function to correctly initialize
regdisplay in case of WIN64EXCEPTIONS.

Commit migrated from https://github.com/dotnet/coreclr/commit/8eb9adbe7f069638c1457b458c2c5a569eaaabf8