Creating the `rpc_misc.py` functional test file to add space for adding tests to a file that doesn't have a lot of coverage.
  - Removing the `getmemoryinfo()` smoke test from wallet basic rather than moving it to keep the wallet decoupled. Feel like testing for reasonable memory allocation values should suffice.
  - Adding coverage for `mallocinfo()`. Introduced standard lib XML parser since the function exports an XML string that describes the current state of the memory-allocation implementation in the caller.

ninja check-functional