Add nooz

nooz/165.feature.rst

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+Add SIGINT protection to our `pdbpp` based debugger subystem such that
+for (single-depth) actor trees in debug mode we ignore interrupts in any
+actor currently holding the TTY lock thus avoiding clobbering IPC
+connections and/or task and process state when working in the REPL.
+
+As a big note currently so called "nested" actor trees (trees with
+actors having more then one parent/ancestor) are not fully supported
+since we don't yet have a mechanism to relay the debug mode knowledge
+"up" the actor tree (for eg. when handling a crash in a leaf actor).
+As such currently there is a set of tests and known scenarios which will
+result in process cloberring by the zombie repaing machinery and these
+have been documented in https://github.com/goodboy/tractor/issues/320.
+
+The implementation details include:
+
+- utilizing a custom SIGINT handler which we apply whenever an actor's
+  runtime enters the debug machinery, which we also make sure the
+  stdlib's `pdb` configuration doesn't override (which it does by
+  default without special instance config).
+- litter the runtime with `maybe_wait_for_debugger()` mostly in spots
+  where the root actor should block before doing embedded nursery
+  teardown ops which both cancel potential-children-in-deubg as well
+  as eventually trigger zombie reaping machinery.
+- hardening of the TTY locking semantics/API both in terms of IPC
+  terminations and cancellation and lock release determinism from
+  sync debugger instance methods.
+- factoring of locking infrastructure into a new `._debug.Lock` global
+  which encapsulates all details of the ``trio`` sync primitives and
+  task/actor uid management and tracking.
+
+We also add `ctrl-c` cases throughout the test suite though these are
+disabled for py3.9 (`pdbpp` UX differences that don't seem worth
+compensating for, especially since this will be our last 3.9 supported
+release) and there are a slew of marked cases that aren't expected to
+work in CI more generally (as mentioned in the "nested" tree note
+above) despite seemingly working  when run manually on linux.