Rename SwitchLocation -> SwitchSlot

[jgallagher]

Followup from #9984 which added the database-level DbSwitchSlot enum, this renames our SwitchLocation enum to SwitchSlot (and renames local variables in many spots, although I'm sure I missed a few). This is a combination of "consistency between Rust types and db types" and "free up the name SwitchLocation which implies both a rack ID + a switch slot".

This bumps the sled-agent and external API versions, but in a wire-compatible way (just a type rename).

[smklein]

LGTM - i understand the most important part of this is changing the externally-facing names, and I think this PR already accomplishes that.

My feedback is basically all nits, but all my comments are about convergence of our many "internal" names for this field, which appear to vary between:

• location
• loc
• slot
• switch_slot

converging on one, as much as possible, would be nice. but I'll defer to your judgement on how much time to spend aligning that, since "database type names" and "API type names" are the ones that matter the most

[jgallagher]

My feedback is basically all nits, but all my comments are about convergence of our many "internal" names for this field

Thanks, this is great - I agree we should make these line up as best we can. I'll grab all the ones you found.