feat(db monitor): adds a new metric speckle_db_tablesize with db table sizes (#2474)

* feat(db queries): adds db query scripts for determining db sizes

* Adds a new metric `speckle_db_tablesize` with db table sizes

* lower case all the file types to provide a combined metric

* group file status count by lower cased file type

* reinstate accidentally deleted metric

* Fix developer script

test-queries/objects-sizes.sql

@@ -0,0 +1,3 @@
+SELECT id, "streamId", "speckleType", "createdAt"::date, pg_column_size(data) / 1024 /1024 || 'MB' AS size, data
+	FROM objects
+	ORDER BY size DESC LIMIT 20;