nix(test): add test suite for observability tests

- Create separate test suite for observability tests

- Create wrapper script `postgrest-test-observability`

- Add to CI and `postgrest-check`

- Move JWT cache tests under observability tests

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

test/observability/fixtures/schema.sql

@@ -0,0 +1,21 @@
+DROP SCHEMA IF EXISTS test;
+
+CREATE SCHEMA test;
+
+SET search_path = test, pg_catalog;
+
+--
+-- Name: authors_only; Type: TABLE; Schema: test; Owner: -
+--
+
+CREATE TABLE authors_only (
+    owner character varying NOT NULL,
+    secret character varying NOT NULL
+);
+
+--
+-- Name: authors_only_pkey; Type: CONSTRAINT; Schema: test; Owner: -
+--
+
+ALTER TABLE ONLY authors_only
+    ADD CONSTRAINT authors_only_pkey PRIMARY KEY (secret);