Start refactoring some business logic into view models

As Element Call grows in complexity, it has become a pain point that our business logic remains so tightly coupled to the UI code. In particular, this has made testing difficult, and the complex semantics of React hooks are not a great match for arbitrary business logic. Here, I show the beginnings of what it would look like for us to adopt the MVVM pattern. I've created a CallViewModel and TileViewModel that expose their state to the UI as rxjs Observables, as well as a couple of helper functions for consuming view models in React code.

This should contain no user-visible changes, but we need to watch out for regressions particularly around focus switching and promotion of speakers, because this was the logic I chose to refactor first.

yarn.lock

@@ -2050,6 +2050,17 @@
     loglevel "^1.8.1"
     rxjs "^7.8.0"
 
+"@livekit/components-core@^0.7.0":
+  version "0.7.0"
+  resolved "https://registry.yarnpkg.com/@livekit/components-core/-/components-core-0.7.0.tgz#1283a34753c8f1bb805b987684a3e29d1bc2eb39"
+  integrity sha512-KwzqnW8V9G+4fXc4gOxpXqQFLpL/kFBn82sYO10zHjHfNKSw4pRj1sDLTWc5UF22W2Z461/bqMtB+3WGB/3Dtg==
+  dependencies:
+    "@floating-ui/dom" "^1.1.0"
+    email-regex "^5.0.0"
+    global-tld-list "^0.0.1139"
+    loglevel "^1.8.1"
+    rxjs "^7.8.0"
+
 "@livekit/components-react@^1.1.0":
   version "1.4.2"
   resolved "https://registry.yarnpkg.com/@livekit/components-react/-/components-react-1.4.2.tgz#f4b09621a244fa832803ca0fc4b200a548dc3b8d"
@@ -2726,6 +2737,14 @@
   resolved "https://registry.yarnpkg.com/@react-hook/latest/-/latest-1.0.3.tgz#c2d1d0b0af8b69ec6e2b3a2412ba0768ac82db80"
   integrity sha512-dy6duzl+JnAZcDbNTfmaP3xHiKtbXYOaz3G51MGVljh548Y8MWzTr+PHLOfvpypEVW9zwvl+VyKjbWKEVbV1Rg==
 
+"@react-rxjs/core@^0.10.7":
+  version "0.10.7"
+  resolved "https://registry.yarnpkg.com/@react-rxjs/core/-/core-0.10.7.tgz#09951f43a6c80892526ac13d51859098b0e74993"
+  integrity sha512-dornp8pUs9OcdqFKKRh9+I2FVe21gWufNun6RYU1ddts7kUy9i4Thvl0iqcPFbGY61cJQMAJF7dxixWMSD/A/A==
+  dependencies:
+    "@rx-state/core" "0.1.4"
+    use-sync-external-store "^1.0.0"
+
 "@react-spring/animated@~9.7.3":
   version "9.7.3"
   resolved "https://registry.yarnpkg.com/@react-spring/animated/-/animated-9.7.3.tgz#4211b1a6d48da0ff474a125e93c0f460ff816e0f"
@@ -3045,6 +3064,11 @@
   resolved "https://registry.yarnpkg.com/@rollup/rollup-win32-x64-msvc/-/rollup-win32-x64-msvc-4.6.1.tgz#45785b5caf83200a34a9867ba50d69560880c120"
   integrity sha512-0zfTlFAIhgz8V2G8STq8toAjsYYA6eci1hnXuyOTUFnymrtJwnS6uGKiv3v5UrPZkBlamLvrLV2iiaeqCKzb0A==
 
+"@rx-state/core@0.1.4":
+  version "0.1.4"
+  resolved "https://registry.yarnpkg.com/@rx-state/core/-/core-0.1.4.tgz#586dde80be9dbdac31844006a0dcaa2bc7f35a5c"
+  integrity sha512-Z+3hjU2xh1HisLxt+W5hlYX/eGSDaXXP+ns82gq/PLZpkXLu0uwcNUh9RLY3Clq4zT+hSsA3vcpIGt6+UAb8rQ==
+
 "@sentry-internal/tracing@7.83.0":
   version "7.83.0"
   resolved "https://registry.yarnpkg.com/@sentry-internal/tracing/-/tracing-7.83.0.tgz#8f69d339569b020c495f8350a8ea527c369586e8"
@@ -5848,6 +5872,11 @@ glob@^7.0.0, glob@^7.1.3, glob@^7.1.4:
     once "^1.3.0"
     path-is-absolute "^1.0.0"
 
+global-tld-list@^0.0.1139:
+  version "0.0.1139"
+  resolved "https://registry.yarnpkg.com/global-tld-list/-/global-tld-list-0.0.1139.tgz#70400a3f3ccac1a19a8184274a1b117bc8a27969"
+  integrity sha512-TCWjAwHPzFV6zbQ5jnJvJTctesHGJr9BppxivRuIxTiIFUzaxy1F0674cxjoJecW5s8V32Q5i35dBFqvAy7eGQ==
+
 globals@^11.1.0:
   version "11.12.0"
   resolved "https://registry.yarnpkg.com/globals/-/globals-11.12.0.tgz#ab8795338868a0babd8525758018c2a7eb95c42e"
@@ -8579,7 +8608,7 @@ run-parallel@^1.1.9:
   dependencies:
     queue-microtask "^1.2.2"
 
-rxjs@^7.5.2, rxjs@^7.8.0:
+rxjs@^7.5.2, rxjs@^7.8.0, rxjs@^7.8.1:
   version "7.8.1"
   resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-7.8.1.tgz#6f6f3d99ea8044291efd92e7c7fcf562c4057543"
   integrity sha512-AA3TVj+0A2iuIoQkWEK/tqFjBq2j+6PO6Y0zJcvzLAFhEFIO3HL0vls9hWLncZbAAbK0mar7oZ4V079I/qPMxg==
@@ -9385,6 +9414,11 @@ use-sidecar@^1.1.2:
     detect-node-es "^1.1.0"
     tslib "^2.0.0"
 
+use-sync-external-store@^1.0.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/use-sync-external-store/-/use-sync-external-store-1.2.0.tgz#7dbefd6ef3fe4e767a0cf5d7287aacfb5846928a"
+  integrity sha512-eEgnFxGQ1Ife9bzYs6VLi8/4X6CObHMw9Qr9tPY43iKwsPw8xE8+EFsf/2cFZ5S3esXgpWgtSCtLNS41F+sKPA==
+
 usehooks-ts@^2.9.1:
   version "2.9.1"
   resolved "https://registry.yarnpkg.com/usehooks-ts/-/usehooks-ts-2.9.1.tgz#953d3284851ffd097432379e271ce046a8180b37"