Allow connecting to an external bitbake server

[cordlandwehr]

Often in commercial environments, developers use a specifically configured Docker container to isolate the Yocto setup more from the (possibly outdated or even not supported) host system or maybe to just enforce a certain native compiler. For such setups, one usually has to do the following steps to run bitbake:

1. start or log in into a container
2. perform "some" operation to initialize a Git credentials cache (or similar) to obtain access to company internal restricted repositories
3. then source the environment and run BitBake Even though all of the above can be put into a wrapper script that is run as a Command Wrapper, I think this is a so common setup that it makes sense to have a dedicated configuration option for such settings where first a login into a container and then a pre-command in that container is needed. By this, one could even put the container lifetime into the hands of VS-code and better isolate against Bitbake failures where the BitBake server is still running but not cleaned up correctly.