multitenant tests: reduce reliance on env vars, use fake cabal run

There's two major parts to this change:

1. cut down on environment variables needed to run the tests:
  - lux parameters that don't change are now in code
  - most remaining parameters have reasonable defaults
  - the only variable that is still required to be set is HASURA_MULTITENANT_SPEC_DB_URL
  - env.sh is no longer needed
2. find a better work-around for the problems running graphql-engine-multitenant
  via cabal run (haskell/cabal#7914), by adding a shell
  script that implements a more correct version of cabal run.

PR-URL: hasura/graphql-engine-mono#3461
GitOrigin-RevId: 0939a79cc45cd3c1c103719552b12099678850dd

Author: robx

cabal.project.freeze

@@ -132,7 +132,6 @@ constraints: any.Cabal ==3.2.0.0,
              any.ekg-wai ==0.1.0.3,
              any.entropy ==0.4.1.6,
              entropy -halvm,
-             any.envy ==2.1.0.0,
              any.erf ==2.0.0.0,
              any.errors ==2.3.0,
              any.exceptions ==0.10.4,

scripts/cabal-run.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+#   cabal-run.sh target args
+#
+# is equivalent to
+#
+#   cabal run target --args
+#
+# except that killing it will also kill the target.
+#
+# https://github.com/haskell/cabal/issues/7914
+
+set -euo pipefail
+
+target="$1"
+shift
+
+echo "building target: ${target}"
+cabal build "$target"
+
+executable=$(cabal list-bin "$target")
+
+exec "$executable" "$@"