This commit makes ThreadMemory a real "forwarder" class by implementing
the missing queue methods: they will just call the corresponding backing
thread method.
To make this patch NFC(*) and not change the behavior of the Python OS
plugin, NamedThreadMemoryWithQueue also overrides these methods to
simply call the `Thread` method, just as it was doing before. This also
makes it obvious that there are missing pieces of this class if it were
to provide full queue support.
(*) This patch is NFC in the sense that all llvm.org plugins will not
have any behavior change, but downstream consumers of ThreadMemory will
benefit from the newly implemented forwarding methods.
07c82b1622