Convert Learner Dashboard to frontend-base

[arbrandes]

Description

Convert the Learner Dashboard MFE to use frontend-base, as per https://github.com/openedx/frontend-base/blob/main/docs/how_tos/migrate-frontend-app.md.

The converted code will remain in a long-lived frontend-base branch.

Dropped features

The following features are removed as part of the conversion:

• Hotjar (DEPR)
• Optimizely (DEPR)
• Segment tracking hooks in the header (DEPR)
• robots.txt (DEPR)
• Notices (DEPR)
• NON_BROWSABLE_COURSES is removed and effectively always true ("Discover New" always shows in the default header) (DEPR)
• Show support email in case of network failure (it couldn't work, as the support email was fetched from the backend... via the network) (DEPR)
• react-helmet (setting favicon and page title) (DEPR)

DEPR tickets will be created and linked above as necessary.

PRs

• refactor: migrate to frontend-base #669

TODO

• Remove undesired features
• Convert basic app structure (site.config, App.tsx, etc)
• Refactor imports
• Implement mechanism for dynamic slot configuration frontend-base#78
• Implement combined app context frontend-base#83
• Implement QueryClientProvider frontend-base#84
• Convert header
• Convert footer
• feat: Prepare for publication to NPM #673
• Publish to NPM as a buildless library
• Include in frontend-template-site as default configuration
• Fix tests
• Test, and if necessary fix, pagination (might be broken due to react-query refactor)
• Redirect unauthenticated users to login
• Paragon 23 (depends on frontend-base support)
• Ongoing: merges with master