feat: legacy to new schema export COMPASS-8798

[paula-stacho]

Description

This is a temporary modal for gentle sunsetting of the legacy schema export. With this in mind, I wanted to not spend too much time on it, so the code might not be the cream of the crop.
Notes:

• the modal is behind the feature flag, to be released together with the new export
• user can choose the legacy or the new behaviour
• the modal shows every time they use the menu item, but there is a checkbox to turn it off

Telemetry will be handled separately.

The tooltips and the background image are nice to have's, I will create a separate ticket for them.

• add tests

Checklist

• New tests and/or benchmarks are included
• Documentation is changed or added
• I have signed the MongoDB Contributor License Agreement (https://www.mongodb.com/legal/contributor-agreement)

Motivation and Context

• Bugfix
• New feature
• Dependency update
• Misc

Open Questions

Dependents

Types of changes

• Backport Needed
• Patch (non-breaking change which fixes an issue)
• Minor (non-breaking change which adds functionality)
• Major (fix or feature that would cause existing functionality to change)

[Anemy]

lgtm, left a couple small questions/suggestions. It will be nice when we can get rid of this flow entirely down the line.

[Anemy]

Calling out that in a branch I'm working on I've updated all the share wording to be export for the internals, so we have some more consistency. In case someone brings it up.