Remove old migration code & Avoid db test image confusion (#2038)

* refact(dbtest): Remove old migration code

This is no longer needed, so we can clean up this
script a bit.

* refact(dbtest): Change test image env var

The existing environment variable clashes with
the one used in the top level Makefile. The new
name prevents confusing behavior when setting
the env var and creating the test database from
the root of the repository.

testing/dbtest/docker/Makefile

@@ -4,8 +4,8 @@ CWD := $(shell pwd)
 DOCKER_ARGS ?= -d
 
 REGISTRY_NAME?=docker.io/hashicorpboundary
-IMAGE_NAME=postgres
-IMAGE_TAG ?= $(REGISTRY_NAME)/$(IMAGE_NAME):11-alpine
+TEST_IMAGE_NAME=postgres
+TEST_IMAGE_TAG ?= $(REGISTRY_NAME)/$(TEST_IMAGE_NAME):11-alpine
 PG_OPTS ?=
 TEST_DB_PORT ?= 5432
 TEST_CONTAINER_NAME ?= boundary-sql-tests
@@ -22,11 +22,11 @@ ${docker-buildxs}: %-buildx:
 	docker buildx build \
 		--platform linux/amd64,linux/arm64 \
 		--push \
-		-t $(REGISTRY_NAME)/$(IMAGE_NAME):$* \
+		-t $(REGISTRY_NAME)/$(TEST_IMAGE_NAME):$* \
 		-f Dockerfile.$* .
 
 database-up:
-	@echo "Using image:                       $(IMAGE_TAG)"
+	@echo "Using image:                       $(TEST_IMAGE_TAG)"
 	@echo "Additional postgres configuration: $(PG_OPTS)"
 	@docker run \
 		$(DOCKER_ARGS) \
@@ -38,7 +38,7 @@ database-up:
 		-e PGDATA=/pgdata \
 		--mount type=tmpfs,destination=/pgdata \
 		-v "$(CWD)/../../../internal/db/schema/migrations":/migrations \
-		$(IMAGE_TAG) \
+		$(TEST_IMAGE_TAG) \
 		-c 'config_file=/etc/postgresql/postgresql.conf' \
 		$(PG_OPTS) 1> /dev/null
 	@echo "Container name:                    $(TEST_CONTAINER_NAME)"