Make opening in an existing instance work outside code-server

I neglected to realize that "".split(":") is an array with "" in it.

Now that the exception handling happens further up there doesn't seem to
be an advantage in having this in a separate method.

It'll always be zero here.

Otherwise it outputs when trying to open a file in an existing instance
externally. Externally there isn't an environment variable to branch on
to skip this line so instead output it with the other info lines in the
child process.

This will allow cliArgs to be only the actual arguments the user passed
which will be used for some logic around opening in existing instances.

- Immediately create ipcMain so it doesn't have to be a function which I
  think feels cleaner.
  - Move exit handling to a separate function to compensate (otherwise
    the VS Code CLI for example won't be able to exit on its own).
- New isChild prop that is clearer than checking for parentPid (IMO).
- Skip all the checks that aren't necessary for the child process (like
  --help, --version, etc).
  - Since we check if we're the child in entry go ahead and move the
    wrap code into entry as well since that's basically what it does.
- Use a single catch at the end of the entry.
- Split out the VS Code CLI and existing instance code into separate
  functions.

Feels more appropriate there to me.

Updates #1729

To fully close that issue see the various TODOs.

Closes #1961

cloud: Rename --coder-bind to --link

See https://stackoverflow.com/a/34881585/4283659

Closes #1538

Integrate Coder Cloud Agent

Closes #1961

🤦

No purpose when all the args are in the args parameter.

We only need configArgs for bindAddrFromAllSources.

See https://github.com/nhooyr/code-server/pull/1/files#r485847134