Switch database 'start_time' to timestamp without time zone

See https://gitlab.ssec.wisc.edu/cspp_geo/geosphere/geosphere-deploy/-/issues/4

and geosphere-mapserver!3 (merged)

This includes a lot of new unit tests.

ci/test_tile_gen_exec.sh

@@ -33,7 +33,7 @@ BASE_WORK_DIR=${BASE_WORK_DIR:-${TMPDIR:-/tmp}}
 base_tmp_dir="__TOBECREATED__"
 
 setup_test() {
-    base_tmp_dir=$(mktemp -d ${BASE_WORK_DIR}/mapserver-tests-XXXXXXX)
+    base_tmp_dir=$(mktemp -d ${BASE_WORK_DIR}/tile-gen-tests-XXXXXXX)
     cd "${base_tmp_dir}"
     chmod 777 .
     echo "Temporary directory: ${base_tmp_dir}"