Package search: find a package without knowing its exact name

[bdbarnett]

mpftp search WORDS finds a package without knowing its exact name: one search across micropython-lib (the index mip reads), the PyDevices index and the Adafruit and community CircuitPython bundles (the manifest each release attaches, which is what circup installs from).

$ mpftp search display text --text --limit 2
adafruit_display_text 5.0.6  [Adafruit CircuitPython Bundle] — Displays text using CircuitPython's displayio.
    mpftp circup adafruit_display_text
adafruit_display_emoji_text 1.0.5  [Adafruit CircuitPython Bundle] — Displayio class for displaying text that contains emoji
    mpftp circup adafruit_display_emoji_text
2 of 5 matches; --limit shows more.

• Results are ranked: the exact name, then names that start with the words, then names that contain them, then descriptions. Case, _, - and spaces don't matter.
• Each result carries its source, version, description and how to install it: the command line, and the RPC method and params behind it. A PyDevices package's line has --index https://PyDevices.github.io/mip, which mip needs to find it.
• The PyDevices index mirrors micropython-lib; a package that is in both at the same version is listed once, from micropython-lib.
• Without --text the answer is JSON. --source, --interpreter and --limit narrow it; the search needs no board.
• Indexes are cached for six hours under ~/.mpftp/package-cache. --refresh fetches them again. Offline, the search runs on the cached copies and says so, or says which index it could not fetch and has no copy of yet.

Search Packages… in the ⋯ menu, in VS Code and in the browser interface, searches the indexes the connected board installs from (micropython-lib and PyDevices on MicroPython, the two bundles on CircuitPython) and installs the result you pick, through the same mip_install / circup_install calls as Install Package.

Tests run on recorded cuts of the four real indexes, so they need no network: parsing, the ranking tiers, mirror dedupe, cache freshness and --refresh, offline with a stale cache and with none, one index down while the others answer, the CLI's flags and the RPC's params. The browser dialog's notes have node tests too.

The roadmap bullet comes out with this; the CHANGELOG has the entry.