gcjob: issue DeleteRange tombstones and then wait for GC

[ajwerner]

Note that this does not change anything about tenant GC.

Fixes https://github.com/cockroachdb/cockroach/issues/70427

Release note (sql change): The asynchronous garbage collection process has been changed such that very soon after dropping a table, index, or database, or after refreshing a materialized view, the system will issue range deletion tombstones over the dropped data. These tombstones will result in the KV statistics properly counting these bytes as garbage. Before this change, the asynchronous "gc job" would wait out the TTL and then issue a lower-level operation to clear out the data. That meant that while the job was waiting out the TTL, the data would appear in the statistics to still be live. This was confusing.

[cockroach-teamcity]

This change is 

[ajwerner]

TFTR!

bors r+

[craig[bot]]

Build failed:

• Bazel Essential CI (Cockroach)

[ajwerner]

The test failure was in //pkg/ui/workspaces/db-console. I can't see how that'd be related, so I'm going to try again.

bors r+

[craig[bot]]

Build succeeded:

• Bazel Essential CI (Cockroach)