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.
