Rename lerc python package to pylerc

[ppoply]

Currently, the lerc python package is available on both Anaconda (through the esri channel) and PyPI with the package name: lerc.

This isn't an issue for users installing the package from PyPI, but on Anaconda, the C++ library is distributed using the same package name (lerc) through conda-forge. This naming conflict may cause functionality breakages in certain environments.

Proposal: Rename the lerc python package to pylerc (Transition by the next lerc release)

The import name will remain the same (ie. import lerc) and for the next release of lerc (v5?), a final version of a lerc python package can be released that has the new pylerc package as a dependency. This way backward compatibility will be handled and existing workflows will remain intact.

cc @scw