Normalize design of search boxes in data explorers, settings UI, and tree view

[MRayermannMSFT]

Ensure consistent location of icons, size of icons, icon direction/type, padding, placeholder texts, etc. across data explorers.

Begin addressing this issue by:

1. Identify all search box UX elements
2. Propose a design that they should all be switched to, or at least the changes that need to be made to make them appear more uniform
3. Cost the work needed for each UX element
4. Share results with the team

## Tasks
- [x] Blob explorer side bar
- [x] Blob container explorer
- [x] File explorer
- [ ] Settings panel
- [ ] Tree view