Search page cleanup

[salty-horse]

• This touches other pages, too: Use <aside> for tipboxes, add a title to the 'create style' tipbox
• Remove duplication in search URL query parsing - the two loops set the same variables, so I removed the duplication, and turned the map into a const.
• Fix undefined variable in /search?game - In helpExtLink(), I think this was a copy-paste error from helpListLink() that needs the $id to expand the section when clicking it.
• Remove unused newSearch function - it was removed in d818146
• Move search form into a function - I think I got everything right. The search box in the bottom sets an id, but it's unused. For some reason, the game search form included all the help text, and I don't think there was any hidden input element there, so I moved it outside, and unindented it (View the commit with "ignore whitespace" to see the actual changes)

[salty-horse]

Renamed to SEARCH_TYPES. Once again, I force-pushed and reflexively rebased onto the latest main, so the "Compare" button offered by Github will show more changes than intended.