[Tagging] Enable taxonomy/tagging feature in MFE by default

[bradenmacdonald]

For this task:

1. Change the default for the Course Authoring MFE so that all tagging/taxonomy/copy-paste features are on by default.
2. (The "Search" feature that uses Meilisearch must still be off by default as it's considered "beta" and has the extra requirement of Meilisearch).
3. In the legacy Studio UI code, disable the "Manage Tags" and tag drawer functionality. Leave the code in place, but have it always disabled, as though the feature flag is always off. (We don't want users using the tagging code in the legacy UI but we need to keep in in place in case there are problems with the Course Authoring MFE and it isn't usable for Redwood)
4. Before merging the PR for (1), work with edx.org to explicitly disable the relevant Waffle flag, so that the tagging/taxonomies feature stays off in the Course Authoring MFE on edx.org until they're ready to launch it.

[bradenmacdonald]

Done via openedx/edx-platform#34633 and openedx/frontend-app-authoring#989