Webdev serve: add an option to pass user data directory to chrome

[annagrin]

Webdev launches chrome using temp profile by default, so the users
cannot use their extensions while debugging. Allow launching chrome
in a window that is signed in as the user's default profile.

Notes:

There seems to be a limitation in chrome - it only uses the existing
session with --user-data-dir. The existing session cannot open a debug
port that dwds needs.

To work around this issue, we copy the default profile to a temporary
directory, and pass it to chrome. That seems to work, but takes time
to copy the profile. Issue a performance warning in that case.

Note that subsequent updates will only update modified files, so the
performance hit becomes smaller over time.

Closes: #1490

[annagrin]

@elliette @grouma I revived my old work on webdev to enable users to login into their chrome account and have access to extensions (ie debug extension). This includes updating the browser_launcher package and code in webdev to copy users directory. We can also use PR as example for other places where dwds is used.

[grouma]

I would hope that the user wouldn't need to pass the data dir. Instead webdev would automatically find and or create a reusable data dir. Is that feasible?

[annagrin]

I would hope that the user wouldn't need to pass the data dir. Instead webdev would automatically find and or create a reusable data dir. Is that feasible?

I am not sure yet (need to figure out how to do that for linux and macos) so I'd prefer this to be done in a separate PR.

[annagrin]

@grouma Looked into adding automatic detection, it looked simple so added it to the same PR. Let's see if the tests would work in the CI.