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/models.go

@@ -3384,6 +3384,10 @@ type ProvisionerJob struct {
 	TraceMetadata  pqtype.NullRawMessage    `db:"trace_metadata" json:"trace_metadata"`
 	// Computed column to track the status of the job.
 	JobStatus ProvisionerJobStatus `db:"job_status" json:"job_status"`
+	// Total length of provisioner logs
+	LogsLength int32 `db:"logs_length" json:"logs_length"`
+	// Whether the provisioner logs overflowed in length
+	LogsOverflowed bool `db:"logs_overflowed" json:"logs_overflowed"`
 }
 
 type ProvisionerJobLog struct {