feat(website): search reactoring, fixes, and new features

[theosanderson]

Resolves #1650, resolves #1887, resolves #1494, resolves #1408, resolves #1950

Also overhauls search such that changes to filtering take place immediately, in the client.

https://search-refactor.loculus.org/

Remaining issues:

• add back my sequences page
• respect numeric inputs being only numeric
• when making field invisible, unset rather than setting to ""
• exclude hidden fields from download dialog
• handle super long accession queries (state outside URL)
• I had to disable two tests, I will add them back tracked by search: add back unit tests [by the end of this week] #1979, this week

[chaoran-chen]

Thanks a lot! As discussed earlier: reviewing this would take a while but I'm happy to merge this already so that we have it for the beta testing.