Add `Arbiter.delete_sockaddr()` to remove addrs

Since stale addrs can be leaked where the actor transport server task
crashes but doesn't (successfully) unregister from the registrar, we
need a remote way to remove such entries; hence this new (registrar)
method.

To implement this make use of the `bidict` lib for the `._registry`
table thus making it super simple to do reverse uuid lookups from an
input socket-address.

setup.py

@@ -41,6 +41,9 @@ setup(
     ],
     install_requires=[
 
+        # discovery subsys
+        'bidict',
+
         # trio related
         # proper range spec:
         # https://packaging.python.org/en/latest/discussions/install-requires-vs-requirements/#id5

tractor/_runtime.py

@@ -40,6 +40,7 @@ from contextlib import ExitStack
 import warnings
 
 from async_generator import aclosing
+from bidict import bidict
 from exceptiongroup import BaseExceptionGroup
 import trio  # type: ignore
 from trio_typing import TaskStatus
@@ -1774,10 +1775,10 @@ class Arbiter(Actor):
 
     def __init__(self, *args, **kwargs) -> None:
 
-        self._registry: dict[
+        self._registry: bidict[
             tuple[str, str],
             tuple[str, int],
-        ] = {}
+        ] = bidict({})
         self._waiters: dict[
             str,
             # either an event to sync to receiving an actor uid (which
@@ -1871,3 +1872,15 @@ class Arbiter(Actor):
         entry: tuple = self._registry.pop(uid, None)
         if entry is None:
             log.warning(f'Request to de-register {uid} failed?')
+
+
+    async def delete_sockaddr(
+        self,
+        sockaddr: tuple[str, int],
+
+    ) -> tuple[str, str]:
+        uid: tuple = self._registry.inverse.pop(sockaddr)
+        log.warning(
+            f'Deleting registry entry for {sockaddr}@{uid}!'
+        )
+        return uid