Support Running Nebula Graph in Non Root mode

[kevinliu24]

Is your feature request related to a problem? Please describe.
Currently Nebulagraph can only be run by the root user in kubernetes. Running as a non root user will result in the error MetaDaemon.cpp:120] Open or create 'pids/nebula-metad.pid': Permission denied since the pids directory is owned by the root user. This was experienced by a customer in the issue below and successfully reproduced inhouse.
vesoft-inc/nebula-operator#544

Describe the solution you'd like
We should allow non-root users to run Nebula by giving them write access to the pids directory and other needed directories when building the metad, graphd and storaged images.

Describe alternatives you've considered

Additional context