Ship packages as ESM only

[jonkoops]

Is this a new component or an extension of an existing one?
This applies to all packages in the PatternFly React repository.

Describe the feature
Instead of shipping PatternFly React packages with a bunch of different module systems (UMD, CommonJS, etc). All packages would be shipped only in the standardized ECMAScript module format.

[jonkoops]

@tlabaj could you mark this as a breaking change?