Soong: Add unbind option to setup_go_workspace_for_soong.sh script

The setup_go_workspace_for_soong now allows the reverse operation
of unbinding the directories of the previous operation. Also,
refactored the script to easily add more directories to bind/unbind
in the future, catch failures on running in subshell commands and
a cleaner way to find the repo top directory.

Bug: b/129407866
Test: Manually tested by running the script on binding and unbinding
the directories. Tested both darwin and linux OS.

Change-Id: I7c93230aeab819ab5747e990e95aa26077071d9e