Impliment datastores to reduce boilerplate

[Cooldude2606]

WIP feature, see #596 for details.

Main Objectives:

• Reduce the number of things to remember when changing values to a single set or setMany call.
• Fully handle the dirty flag within the class, no more checking before saving or setting after changes.
• Create an interface that allows for formats other than JSON to be used.
• Allow plugins to use the class without forcing the use of subscribable values.

Decisions Made:

• There are two base classes BaseDatastore and DatastoreProvider one is an interface to plugins / controller the other provides the abilty to save and load data.
• There are three providers implemented:
  • MemoryDatastoreProvider offers no abilty to save and load and is designed for testing or when saving is not required.
  • JsonDatastoreProvider saves the data as a JSON object, has the abilty to migrate and finalise data.
  • JsonIdDatastoreProvider saves the data as a JSON array where objects store their own id.
• There are two datastores implemented:
  • Datastore the basic datastore that functions like a map.
  • SubscribableDatastore a datastore specialised to handle SubscribableValue
• Get has readonly and mutable variations to nudge developers to only mutate when needed and to always call set.
• The ModStore and UserManager have not been changed due to their complexity.

[codecov]

Codecov Report

Attention: Patch coverage is 65.26946% with 58 lines in your changes are missing coverage. Please review.

Project coverage is 76.64%. Comparing base (78a9f73) to head (94a07b5).
Report is 28 commits behind head on master.

❗ Current head 94a07b5 differs from pull request most recent head 8b823a5

Please upload reports for the commit 8b823a5 to get more accurate results.

Files	Patch %	Lines
packages/lib/src/datastore.ts	64.51%	32 Missing and 1 partial ⚠️
packages/controller/src/Controller.ts	55.81%	19 Missing ⚠️
packages/controller/controller.ts	0.00%	2 Missing ⚠️
packages/controller/src/HostConnection.ts	88.23%	2 Missing ⚠️
packages/controller/src/InstanceInfo.ts	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #629      +/-   ##
==========================================
- Coverage   76.82%   76.64%   -0.19%     
==========================================
  Files         106      107       +1     
  Lines       10059    10070      +11     
  Branches     1664     1665       +1     
==========================================
- Hits         7728     7718      -10     
- Misses       1797     1824      +27     
+ Partials      534      528       -6     

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