This is to match the other tests that create temp directories. It also
lets you clean up test temp directories all at once separately from
other non-test temporary directories.

Just to limit all the noise from code-server's startup output.

It errors that jest is not defined so put it behind a function instead
of immediately creating the mock (this is probably a better pattern
anyway).

The constant tests had to be reworked a little. Since the logger mock is
hoisted it runs before createLoggerMock is imported. I moved it into a
beforeAll which means the require call also needed to be moved
there (since we need to mock the logger before requiring the constants
or it'll pull the non-mocked logger).

This means getPackageJson needs to be a let and assigned afterward. To
avoid having to define a type for getPackageJson I just added a let var
set to the type of the imported constants file and modified the other
areas to use the same paradigm.

I also replaced some hardcoded strings with the mocked package.json
object.