Replace usage of pkg_resources with importlib_resources

[khmikkelsen]

Replace pkg_resources with importlib_resources as ytmusicapi's usage is limited to the scope of importlib_resources's, and pkg_resources have issues related to python 3.9 with LegacyVersion being deprecated and defaulting to this as mentioned in:

• import pkg_resources triggers a DeprecationWarning on Python 3.9 pypa/packaging#368
• Remove support for LegacyVersion pypa/setuptools#2497
• import pkg_resources triggers a DeprecationWarning on Python 3.9 pypa/setuptools#2466
• Remove support for LegacyVersion pypa/setuptools#2497
• Drop LegacySpecifier and LegacyVersion pypa/packaging#407

While the issue has been known for a while, fixes are not merged yet.
Motivation for this issue: AppDaemon/appdaemon#1336

[sigma67]

I like your suggestion to use importlib_resources, but it requires an additional dependency for older Python versions which wasn't needed before. I've chosen to go with an alternate approach that will eliminate the need for pkg_resources.