…mpotent (#5465)

* null out _unsubscribe after unsubscription

Fixes #5464

* test: add idempotent unsubscribe tests

* fix: null the subscription ctor teardown

* refactor: use delete to remove the member

* refactor: delete _unsubscribe only if it exists

* refactor: replace delete with hasOwnProperty etc

* refactor: use _ctorUnsubscribe flag

Co-authored-by: Nicholas Jamieson <nicholas@cartant.com>

Type fix: Changed intrerval to interval

this is the duplicate of #5610, it is refactoring to ensure outer values are not retained when they do not have to be. It needs to be done in a separate PR because the branches diverge just enough to require it. This PR also has some mild, internal type fixes.

Closes #5635

* build(actions): setup initial gh actions script

* build(actions): include node.js 14

* test(api): update fixtures

* build: Fix api_guardian params

Co-authored-by: Ben Lesh <ben@benlesh.com>

* test(ReplaySubject): add failing tests

* fix(ReplaySubject): don't buffer next if stopped

* chore: remove VSCode-added lodash import

Oh, FFS, now I've done it.

Co-authored-by: Jan-Niklas Wortmann <jan-niklas.wortmann@evorait.com>

* fix(shareReplay): handle possible memory leaks

* test: add shareReplay leak test

* style(shareReplay): fix linting issues

* chore: fix typescript@latest CI failure

Co-authored-by: Nicholas Jamieson <nicholas@cartant.com>