Introduce new /$DB/-/query endpoint, soft replaces /$DB?sql=... (#2363)

* Introduce new default /$DB/-/query endpoint
* Fix a lot of tests
* Update pyodide test to use query endpoint
* Link to /fixtures/-/query in a few places
* Documentation for QueryView

---------

Co-authored-by: Simon Willison <swillison@gmail.com>

tests/test_crossdb.py

@@ -25,7 +25,8 @@ def test_crossdb_join(app_client_two_attached_databases_crossdb_enabled):
       fixtures.searchable
     """
     response = app_client.get(
-        "/_memory.json?" + urllib.parse.urlencode({"sql": sql, "_shape": "array"})
+        "/_memory/-/query.json?"
+        + urllib.parse.urlencode({"sql": sql, "_shape": "array"})
     )
     assert response.status == 200
     assert response.json == [
@@ -67,9 +68,10 @@ def test_crossdb_attached_database_list_display(
 ):
     app_client = app_client_two_attached_databases_crossdb_enabled
     response = app_client.get("/_memory")
+    response2 = app_client.get("/")
     for fragment in (
         "databases are attached to this connection",
         "<li><strong>fixtures</strong> - ",
-        "<li><strong>extra database</strong> - ",
+        '<li><strong>extra database</strong> - <a href="/extra+database/-/query?sql=',
     ):
         assert fragment in response.text