PostgreSQL: Migrate to React (#52831)

- Migrate Postgres query editor to react
- Add support for field aliasing in SELECT clauses to SQL based datasources

Co-authored-by: Kyle Cunningham <kyle@codeincarnate.com>
Co-authored-by: Oscar Kilhed <oscar.kilhed@grafana.com>

public/app/plugins/datasource/postgres/postgresMetaQuery.ts

@@ -0,0 +1,41 @@
+export function getVersion() {
+  return "SELECT current_setting('server_version_num')::int/100 as version";
+}
+
+export function getTimescaleDBVersion() {
+  return "SELECT extversion FROM pg_extension WHERE extname = 'timescaledb'";
+}
+
+export function showTables() {
+  return `select quote_ident(table_name) as "table" from information_schema.tables
+    where quote_ident(table_schema) not in ('information_schema',
+                             'pg_catalog',
+                             '_timescaledb_cache',
+                             '_timescaledb_catalog',
+                             '_timescaledb_internal',
+                             '_timescaledb_config',
+                             'timescaledb_information',
+                             'timescaledb_experimental')
+      and table_type = 'BASE TABLE' and ${buildSchemaConstraint()}`;
+}
+
+export function getSchema(table?: string) {
+  return `select quote_ident(column_name) as "column", data_type as "type"
+    from information_schema.columns
+    where quote_ident(table_name) = '${table}'`;
+}
+
+function buildSchemaConstraint() {
+  // quote_ident protects hyphenated schemes
+  return `
+          quote_ident(table_schema) IN (
+          SELECT
+            CASE WHEN trim(s[i]) = '"$user"' THEN user ELSE trim(s[i]) END
+          FROM
+            generate_series(
+              array_lower(string_to_array(current_setting('search_path'),','),1),
+              array_upper(string_to_array(current_setting('search_path'),','),1)
+            ) as i,
+            string_to_array(current_setting('search_path'),',') s
+          )`;
+}