fix(coderd): add blocking GetProvisionerJobByIDWithLock for workspace build cancellation (#19737)

Closes https://github.com/coder/internal/issues/885

Adds a new database method GetProvisionerJobByIDWithLock that uses FOR
UPDATE without SKIP LOCKED to fix workspace build cancellation returning
500 errors when jobs are locked.

coderd/database/queries/provisionerjobs.sql

@@ -55,6 +55,17 @@ WHERE
 FOR UPDATE
 SKIP LOCKED;
 
+-- name: GetProvisionerJobByIDWithLock :one
+-- Gets a provisioner job by ID with exclusive lock.
+-- Blocks until the row is available for update.
+SELECT
+	*
+FROM
+	provisioner_jobs
+WHERE
+	id = $1
+FOR UPDATE;
+
 -- name: GetProvisionerJobsByIDs :many
 SELECT
 	*