Add Disable Embeddings Mode

[PaulHax]

Trigger show/hide embeddings by CLI arg and/or GUI.

When embeddings is disabled:

• don't compute embeddings
• hide sidebar embedding parameters card

If embeddings are re-enabled by GUI, compute embeddings and plot automatically.

[alesgenova]

Fixed to an extent in #187

• If the embeddings feature is disabled, then it will not be visible in the UI, nor the embeddings will be computed.
• If embeddings is enabled, there is a new toggle switch and shows/hides the embeddings plot from the UI.