[PATCH v2 0/8] MR1629: ntdll: Finish heap refactoring in preparation for LFH support.

[Rémi Bernon (＠rbernon)]

Cleaning up and splitting subheap creation helpers and free block merge logic.

Should be the last refactoring needed before LFH specific changes, as implemented in https://gitlab.winehq.org/wine/wine/-/merge_requests/1628.

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  v2: ntdll: Keep subheap parent heap pointer and check for mismatches.
      ntdll: Move the insertion of the first block out of create_subheap.
      ntdll: Split create_free_block into block_init_free / insert_free_block.
      ntdll: Merge prev and next free heap blocks in heap_free_block.
      ntdll: Split heap blocks before creating or resizing used block.
      ntdll: Clear BLOCK_FLAG_PREV_FREE flag out of shrink_used_block.
      ntdll: Move heap allocation and initialization into RtlCreateHeap.
      ntdll: Split heap region memory allocation to allocate_region helper.

https://gitlab.winehq.org/wine/wine/-/merge_requests/1629