Fuzzy finder improvements

Created by: olafurpg

Following up from a call with @limitedmage, opening this issue to track things that can be improved after merging #20921

Blocking GA

• Iron out design, pending proposal https://www.figma.com/file/ZYu2iiTp4AmnHDXf9EX2sY/File-fuzzy-find?node-id=1%3A6549&viewport=2392%2C586%2C1 (merged PR https://github.com/sourcegraph/sourcegraph/pull/21876 )
• Optimize "download files" step on the backend. It currently takes 10-20 seconds in the chromium repo to download all files. Fixed in progress https://github.com/sourcegraph/sourcegraph/pull/21422
• Be more case insensitive in smaller repos (<25k files). Fixed in #21361
• Stop using cache storage. Pending fix https://github.com/sourcegraph/sourcegraph/pull/21550
• Improve accessibility (PR https://github.com/sourcegraph/sourcegraph/pull/21919, #22054)
• Don't insert git SHA into link URLs when on the default branch (pending PR https://github.com/sourcegraph/sourcegraph/pull/22133)
• Fix the bug that causes files to get re-downloaded when going from repo view to blob view (easy to reproduce in chromium/chromium repo). (pending PR https://github.com/sourcegraph/sourcegraph/pull/22133)

Non-blocking

• Consider using different keyboard shortcut that is also active while the search bar is focused. (superseded by https://github.com/sourcegraph/sourcegraph/issues/22229 )
• Make focusIndex state persistent across blob views (superseded by https://github.com/sourcegraph/sourcegraph/issues/22221 )
• Make dark theme less dark (superseded by https://github.com/sourcegraph/sourcegraph/issues/22222)
• (high priority) Remove fileAnchor?.click() DOM manipulation https://github.com/sourcegraph/sourcegraph/pull/20921/files#r637086203 (superseded by https://github.com/sourcegraph/sourcegraph/issues/22223)
• Address non-blocking review comments from https://github.com/sourcegraph/sourcegraph/pull/21876#pullrequestreview-678690607
• turn renderFuzzyResult method into a component, or remove JSX.Element logic. https://github.com/sourcegraph/sourcegraph/pull/20921/files#r637092526 (superseded by https://github.com/sourcegraph/sourcegraph/issues/22226 )
• Remove fuzzyFinder=debug query parameter once experimentalFeature.fuzzyFinder is supported on dotcom
• Use theme-aware CSS variables for HighlightedText yellow and black colors
• Consider using <mark> for the highlighted section instead of <span> for highlighted result items
• Mock graphql query to make it easier to test - Use BEM notation in CSS
• Use reach <Dialogue component instead of hand-written modal
• Fine-tune bloom filter false positive ratio for ideal latency/memory-usage balance.
• Remove usage of global eslint-disable
• Inline offsetSum at call site (wontfix)
• Inline properties into FuzzyModalProps
• Rename CaseSensitiveFuzzySearch to WordSensitiveFuzzySearch because "case insensitive" would allow the query "bar" to match "Foobar" whereas the current implementation does not match because it requires the query to start a word
• Add storybook tests
• Investigate why the query "attributes" in sourcegraph/sourcegraph doesn't return results for the filename ".gitattributes"

FYI @novoselrok