feat: cancel pending enter/change hooks on location change

[alisd23]

Fix for #3220.

• Transition manager keeps track of pending async (or sync) hooks (for onEnter and onChange).
• When new transition starts, redirects from pending async hooks are ignored, fixing the unexpected behaviour in Redirects back to previous route call onLeave but not onEnter #3220
• When the hook completes, it is removed from the pending list

This prevents a redirect from old transitions happening. If a new transition occurs after an async hook with a redirect starts, the new location should take precedence, so the redirect is ignored.

See new tests for situations where this might occur

Also fixed npm tasks on windows again whilst I was there 😄

[timdorr]

I've been over this in my head a few times. I don't think I can punch any holes in it right now, so I think this is good as-is. Of course, when we push 3.0 I may end up eating my words :P

[alisd23]

@timdorr It's alright I'll take half the blame 😆