- Removed `getFreePort` as its use is always a race condition. Change
  all uses of it to retrive the port after listening

- Added `getPortFrom` as a helper function to read a port from a stream

- Remove `Cluster.ownerRef` as it is outdated and no longer needed for 5.0

- Remove `Cluster.enabled`, no longer needed because of above

- Removed `Cluster.init`, moved its contents into `Cluster.constructor`
  as nothing in that function is asyncronous. Currently only being run
  on `main` as a stop gap until `renderer` gets its own version of
  `Cluster`

- Refactored `LensProxy` so as to prevent `pty.node` (a NodeJS
  extension) being included in `webpack.extension.ts`'s run

- Removed the passing around of the proxy port as that can now be
  accessed from an instance of `LensProxy`

- purge ContextHandler's cache on disconnect
Co-authored-by: Sebastian Malton <sebastian@malton.name>