chore(MPL): Rename MPL Python package

[lucasmcdonald3]

Issue #, if available:

Description of changes:

Three changes:

• Rename MPL from aws-cryptographic-materialproviders to aws-cryptographic-material-providers, same for _
• Merge from master; this gets this commit

It would be great if these could be separate PRs, but they can't. CI will only pass with both of these changes.

The third change could be its own PR, but it's just one line:

• Provide correct CMM in a required EC CMM example test

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Check any applicable:

• Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.

[josecorella]

lgtm