Remove `AllocLHeap`. (#33402)

Remove `AllocLHeap`. (#33402)

* The main difference of `AllocLHeap` is that it uses per-heap acontext instead of per-thread. There is no advantage in that and results in allocations under-reported in `GetAllocatedBytesForCurrentThread`

This change unifies to one allocation entry point - `Alloc` (and its `AllocAlign8` variety)

* Removed AllocAlign8

* PR feedback - some refactoring to merge duplicate calls to `Alloc`

* Splited an `ifdef/else`  in two to not cross code blocks.

* No need to update `GC_INTERFACE_MAJOR_VERSION` more than once per release. And we already did for this one.