**- Why I did it**
To enable running Pytest unit tests before building the Python 3 sonic-platform-common package
**- How I did it**
- Add Python 3 sonic-config-engine package as a dependency of Python 3 sonic-platform-common package (needed for both runtime and unit tests)
- No longer disable unit tests when building Python 3 sonic-platform-common package
As part of consolidating all common Python-based functionality into the new sonic-py-common package, this pull request:
1. Redirects all Python applications/scripts in sonic-buildimage repo which previously imported sonic_device_util or sonic_daemon_base to instead import sonic-py-common, which was added in https://github.com/Azure/sonic-buildimage/pull/5003
2. Replaces all calls to `sonic_device_util.get_platform_info()` to instead call `sonic_py_common.get_platform()` and removes any calls to `sonic_device_util.get_machine_info()` which are no longer necessary (i.e., those which were only used to pass the results to `sonic_device_util.get_platform_info()`.
3. Removes unused imports to the now-deprecated sonic-daemon-base package and sonic_device_util.py module
This is the next step toward resolving https://github.com/Azure/sonic-buildimage/issues/4999
Also reverted my previous change in which device_info.get_platform() would first try obtaining the platform ID string from Config DB and fall back to gathering it from machine.conf upon failure because this function is called by sonic-cfggen before the data is in the DB, in which case, the db_connect() call will hang indefinitely, which was not the behavior I expected. As of now, the function will always reference machine.conf.
Both python2 and python3 wheels being built out of the same
source directory can interfere with each other when
SONIC_BUILD_JOBS > 1.
Signed-off-by: Greg Paussa <greg.paussa@broadcom.com>