Fix OOM edge case in interleaved LoaderHeap (#81602)

Fix OOM edge case in interleaved LoaderHeap (#81602)

When the `CommitPages` in `GetMoreCommittedPages` fails, which can
happen due to OOM, the `m_pPtrToEndOfCommittedRegion` was already
updated from the end of the code page to the end of the data page.
So if another allocation request comes to the heap, we think there is
one extra page of space left and end up allocating region that crosses
the code / data page boundary. And later we crash when initializing
precodes that were allocated by this request.

This issue was discovered by a Roslyn CI test that loaded assemblies
into non-collectible AssemblyLoadContext instances and ended up jitting
so many methods that the maximum number of mappings on Linux (65535 by
default) got exceeded and mmap failed.

This change fixes it by moving the `m_pPtrToEndOfCommittedRegion` only
in the success case.