☂️ Migrate `GraphProvider` to `BoardServer`

[paullewis]

Still to do

• [ ] Replace Providers in VE with Board Servers (ensure updates to boards are emitted to nav etc)
• [ ] Remove old Provider sources

Done

• [x] Update Provider logic to use Board Servers (add, remove, etc)
• [x] Update Remote Board Server with /me request
• [x] Tidy Extension code
• [x] Create Remote Board Server
• [x] Create IDB Board Server
• [x] Create Examples Board Server
• [x] Create FileSystem Board Server
• [x] Migrate IDB Graph Providers to IDB Board Server
• [x] Migrate Remote Graph Providers to Remote Board Server
• [x] Migrate Example Graph Providers to Examples Board Server
• [x] Migrate FileSystem Graph Providers to FileSystem Board Server

Later

• [ ] Add Board Server migration utilities & UI