use sphinx-design directives instead of sphinx-panels

[cosmicBboy]

Why are the changes needed?

We are currently using sphinx-panels for various documentation elements like dropdowns and tabs. However, sphinx-panels is no longer maintained and is restricting the version of sphinx we use to 4.5.0. The up-to-date solution for this is sphinx-design.

NOTE: We'll have to merge the related PRs in the following order:

1. use sphinx-design directives instead of sphinx-panels #2364, Use sphinx design instead of sphinx panels flytesnacks#1652, use sphinx-design directives instead of sphinx-panels flytectl#471
2. Use sphinx design instead of sphinx panels flyte#5254

What changes were proposed in this pull request?

This PR:

• Makes changes to the docs to use sphinx-design directives
• Cleans up API docs to leverage the upgraded furo version that displays the right sidebar

How was this patch tested?

Build the docs locally:

Make sure you have the sphinx-design branch checked out in the flytekit, flytesnacks, and flytectl repo. Then build the docs in the flyte repo like so:

FLYTEKIT_LOCAL_PATH=~/git/flytekit FLYTESNACKS_LOCAL_PATH=~/git/flytesnacks FLYTECTL_LOCAL_PATH=~/git/flytectl make docs

[cosmicBboy]

FYI the Monodocs build test is expected to fail. Will need to merge all of the flyte PR flyteorg/flyte#5254 for this to pass on subsequent PRs to this repo.