Allocate string literals on frozen segments (#49576)

Allocate string literals on frozen segments (#49576)

* Naive implementation of FrozenObjectHeap

* Add RegisterFrozenSegment

* Add lock

* Update branch, fix asserts

* Ignore collectible assemblies, fix build

* Rename bAppDomainWontUnload to bIsCollectible

* Address feedback

* Fix more asserts not expecting TYP_REF constants being non zero

* move check to IsEphemeral

* Implement commit-on-demand

* bump FOH_COMMIT_PAGES

* Unix's ClrVirtualAlloc seems to be non-aligned

* Multiple frozen segments

* Fix assert in assertionprop.cpp

* Handle string.Empty (it used to be ignored)

* Address Maoni's feedback:
1) Rename FrozenObjectHeap to FrozenObjectSegment since it represents a single segment
2) Remove unnecessary config knobs and leave only turn off/on one

* heap -> segment in comments

Co-authored-by: Jan Kotas <jkotas@microsoft.com>
Co-authored-by: Andy Ayers <andya@microsoft.com>