Cleanup: Get rid of server.core_propagates (#11572)

1. Get rid of server.core_propagates - we can just rely on module/call nesting levels
2. Rename in_nested_call  to execution_nesting and update the comment
3. Remove module_ctx_nesting (redundant, we can use execution_nesting)
4. Modify postExecutionUnitOperations according to the comment (The main purpose of this PR)
5. trackingHandlePendingKeyInvalidations: Check the nesting level inside this function
