release-20.2: sql: fix bug where bad mutation job state could block dropping tables

[thoszhang]

Backport:

• 1/1 commits from "sql: resolve error due to drop table after schema change in same txn" (sql: resolve error due to drop table after schema change in same txn #56589)
• 1/1 commits from "sql: fix bug where bad mutation job state could block dropping tables" (sql: fix bug where bad mutation job state could block dropping tables #57836)

Please see individual PRs for details.

/cc @cockroachdb/release

[cockroach-teamcity]

This change is 

[thoszhang]

The race detector does not like this test. Let me fix it.

[thoszhang]

diff --git a/pkg/sql/schema_changer_test.go b/pkg/sql/schema_changer_test.go
index d45d242e9f..163da27d2a 100644
--- a/pkg/sql/schema_changer_test.go
+++ b/pkg/sql/schema_changer_test.go
@@ -6132,7 +6132,7 @@ INSERT INTO t.test VALUES (1, 2), (2, 2);
        g := ctxgroup.WithContext(ctx)
        g.GoCtx(func(ctx context.Context) error {
                // Try to create a unique index which won't be valid and will need a rollback.
-               _, err = sqlDB.Exec(`CREATE UNIQUE INDEX i ON t.test(v);`)
+               _, err := sqlDB.Exec(`CREATE UNIQUE INDEX i ON t.test(v);`)
                assert.Regexp(t, "violates unique constraint", err)
                return nil
        })

Should be fine now.

[ajwerner]

Reviewed 2 of 2 files at r1, 2 of 2 files at r2.
Reviewable status: complete! 1 of 0 LGTMs obtained

[thoszhang]

This is hitting #51544. I'm just going to re-run the tests.