le/symbols as weak map keys

[leoelm]

Issue number of the reported bug or feature request: microsoft#52534

Describe your changes
Add type support for symbol to WeakMap, WeakSet, WeakRef and FinalizationRegistry. This has been achieved by retrospectively introducing the interface WeakKeyTypesStore which then composes the type WeakKeyTypes. In previous es versions this custom type will only support object, however expanding the interface to also support symbol has been done in ES2023.

Testing performed
To test the feature addition, WeakMap, WeakSet, WeakRef and FinalizationRegistry and all their member functions have been tested using symbol for the relevant inputs to prove failure in versions preceding es2023 and show it to be working in ES2023.

[acutmore]

Thank you @leoelm this is fantastic!

I've left just a few small comments. Feel free to IB me if want to chat over any of them in person/on a call.

Also feel free to post a link to the PR in the TypeScript contributors IB pchat if you'd like to share your progress.

[acutmore]

Thanks for making those extra changes. They made me notice a few other little things we can do next. Feel free to IB or put in a APPT if want to pair up on any changes.

[acutmore]

This is looking great. I just spotted a few other small places we probably want to update:

• WeakMap.prototype.add comment says the value must be an object: ref
• WeakMap constructor and prototype default to object instead of WeakKey: ref
• WeakSet method comments mention object ref & ref