Closes #20391

### Summary
This adds a persistence layer to the command palette so that usages can
persist after Zed is closed and re-opened.

The current "usage" algorithm is unchanged, e.g.:
- Sorts by number of usages descending (no recency preference)
- Once a user's query is active, removes these suggestions in favor of
fuzzy matching

There are some additional considerations in order to keep the DB from
growing uncontrollably (and to make long-term use ergonomic):
- The "invocations" count handles max values (though at u16, it seems
unlikely a user will deal with this)
- If a command is un-invoked for more than a month, it stops being
considered a recent usage, and its next update will update its usages
back to 1

### Future Considerations
- Could make the "command expiry" configurable in settings, so the user
can decide how long to hold onto recent usages
- Could make a more sophisticated algorithm which balances recency and
total invocations - e.g. if I've used COMMAND_A 100 times in the last
month, but COMMAND_B 10 times today, should COMMAND_B actually be
preferred?
- Could do preferential fuzzy-matching against these matches once the
user starts a query.

Release Notes:

- Added persistent history of command palette usages.

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Co-authored-by: Peter Finn <mastion11@gmail.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>