fix: add constraint and runtime check for provisioner logs size limit (#18893)

This PR sets a constraint of 1MB on the provisioner job logs written to
the database. This is consistent with the constraint we place on
workspace agent logs:
https://github.com/coder/coder/blob/4ac6be6d835dc36c242e35a26b584b784040bf28/coderd/database/dump.sql#L2030

It also adds a message printed to the front end about the provisioner
log overflow, and updates the message printed to the front end when
workspace startup logs exceed the max, as it was causing some customers
to think their startup script had failed to run.

coderd/database/migrations/000355_add_provisioner_logs_overflowed.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE provisioner_jobs DROP COLUMN logs_length;
+ALTER TABLE provisioner_jobs DROP COLUMN logs_overflowed;

coderd/database/migrations/000355_add_provisioner_logs_overflowed.up.sql

@@ -0,0 +1,6 @@
+ -- Add logs length tracking and overflow flag, similar to workspace agents
+  ALTER TABLE provisioner_jobs ADD COLUMN logs_length integer NOT NULL DEFAULT 0 CONSTRAINT max_provisioner_logs_length CHECK (logs_length <= 1048576);
+  ALTER TABLE provisioner_jobs ADD COLUMN logs_overflowed boolean NOT NULL DEFAULT false;
+
+  COMMENT ON COLUMN provisioner_jobs.logs_length IS 'Total length of provisioner logs';
+  COMMENT ON COLUMN provisioner_jobs.logs_overflowed IS 'Whether the provisioner logs overflowed in length';