[DO NOT MERGE] convert to outline-apps repository, approach #2: multi-workspace w/ root utility CLI

[daniellacosse]

This approach, instead of trying to have one big root NPM workspace (traditional monorepo), opts to have several non-overlapping workspaces co-exist in the same repository.

It currently looks like this: https://github.com/Jigsaw-Code/outline-client/tree/daniellacosse/convert_to_outline_apps_2

Tradeoffs:

• Pro: Much easier to combine our existing repositories this way.
• Pro: Fewer overall changes (see approach #1).
• Pro: Easier for different languages to live side-by-side in their own "workspace" concepts (though we don't need or really even want to encourage this, it's a nice to have)
• Pro: Can mix and match different workspaces and versions of node (like use yarn alongside npm, though we probably want to avoid this and have)
• Con: We'll need a root command line utility to more easily interact with everything (can't rely on third-party workspace tools alone).
• Con: Multiple copies of different node dependencies will need to be downloaded, but hopefully the CLI can help there eventually
• Con: shared_infrastructure is a bit more awkward to share between workspaces, but we can probably make it work with the file: syntax
• Is there anything I'm not thinking of?

Current Issues:

• do we need a root third_party folder?
• do we need a root docs folder to preserve the invitation-instructions.md link?

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (3d68446) 36% compared to head (8b3108b) 36%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1693   +/-   ##
======================================
  Coverage      36%     36%           
======================================
  Files          45      45           
  Lines        2749    2749           
  Branches      312     312           
======================================
  Hits         1006    1006           
  Misses       1743    1743           

Flag	Coverage Δ
apple	15% <ø> (ø)
ios	15% <ø> (ø)
macos	15% <ø> (ø)
unittests	36% <ø> (ø)
www	45% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...AppleLib/Sources/OutlineTunnel/OutlineTunnel.swift	67% <ø> (ø)
...Lib/Sources/OutlineTunnel/OutlineTunnelStore.swift	29% <ø> (ø)
...ineAppleLib/Sources/OutlineTunnel/OutlineVpn.swift	0% <ø> (ø)
...OutlineAppleLib/Sources/OutlineTunnel/Subnet.swift	84% <ø> (ø)
...ources/PacketTunnelProvider/PacketTunnelProvider.m	0% <ø> (ø)
...ib/Tests/OutlineTunnelTest/OutlineTunnelTest.swift	100% <ø> (ø)
outline_client/src/infrastructure/custom_error.ts	100% <ø> (ø)
...utline_client/src/infrastructure/memory_storage.ts	62% <ø> (ø)
...tline_client/src/infrastructure/timeout_promise.ts	41% <ø> (ø)
outline_client/src/www/TODO.spec.ts	71% <ø> (ø)
... and 16 more

... and 38 files with indirect coverage changes

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