(chore) rename "repo {add|update|delete}-kvp" to "repo {add|update|delete}-metadata"
Created by: erzhtor
Part of https://github.com/sourcegraph/pr-faqs/issues/96. Related https://github.com/sourcegraph/sourcegraph/pull/50908.
Test plan
- make sure that both versions work the same
$ go run ./cmd/src repos {add|update|delete}-kvp
$ go run ./cmd/src repos {add|update|delete}-metadata