Optimizations to the Nexus schema tests (#8271)

This PR optimizes several of the Nexus schema tests:

- It uses a "baseline" version of dbinit.sql to avoid scaling linearly
with the number of schema changes. It adds the `cargo xtask schema
generate-base` command to help pull down this baseline.
- This PR also adds `cargo xtask schema old-migrations` to assist with
cleaning up old migrations that are before the "baseline", and are no
longer supported.
- It changes a few of the schema tests to compare "baseline" -> "latest"
versions, rather than applying all schema changes that have ever been
created.

```
 $ cargo nt -p omicron-nexus -- integration_tests::schema
 ...
        PASS [   2.152s] omicron-nexus::test_all integration_tests::schema::dbinit_version_matches_version_known_to_nexus
        PASS [   8.946s] omicron-nexus::test_all integration_tests::schema::nexus_applies_update_on_boot
        PASS [  10.831s] omicron-nexus::test_all integration_tests::schema::compare_table_differing_constraint
        PASS [  10.861s] omicron-nexus::test_all integration_tests::schema::compare_sequence_differing_increment
        PASS [  10.997s] omicron-nexus::test_all integration_tests::schema::compare_index_creation_differing_columns
        PASS [  11.043s] omicron-nexus::test_all integration_tests::schema::compare_view_differing_where_clause
        PASS [  11.075s] omicron-nexus::test_all integration_tests::schema::compare_table_differing_not_null_order
        PASS [  11.111s] omicron-nexus::test_all integration_tests::schema::compare_index_creation_differing_where_clause
        PASS [   8.621s] omicron-nexus::test_all integration_tests::schema::update_since_base_has_idempotent_up
        PASS [   8.008s] omicron-nexus::test_all integration_tests::schema::validate_data_migrations
        PASS [  30.662s] omicron-nexus::test_all integration_tests::schema::nexus_cannot_apply_update_from_unknown_version
        PASS [  23.131s] omicron-nexus::test_all integration_tests::schema::validate_migration_from_base_version
────────────
     Summary [  34.713s] 12 tests run: 12 passed, 604 skipped
```

Fixes #10005

Author: smklein

.github/buildomat/build-and-test.sh

@@ -178,6 +178,13 @@ fi
 banner doctest
 ptime -m timeout 1h cargo test --doc --locked --verbose --no-fail-fast
 
+# Verify that old migrations have been removed.
+#
+# We do this after the main build, so the dependencies of "cargo xtask schema"
+# have already been built, which makes this cheap(er).
+banner "check schema migration cleanup"
+ptime -m cargo xtask schema old-migrations
+
 # Build the live-tests.  This is only supported on illumos.
 # We also can't actually run them here.  See the README for more details.
 if [[ $target_os == "illumos" ]]; then

Cargo.lock

@@ -53,6 +53,7 @@ members = [
     "dev-tools/releng",
     "dev-tools/repl-utils",
     "dev-tools/repo-depot-standalone",
+    "dev-tools/schema",
     "dev-tools/xtask",
     "dns-server",
     "dns-server-api",
@@ -230,6 +231,7 @@ default-members = [
     "dev-tools/releng",
     "dev-tools/repl-utils",
     "dev-tools/repo-depot-standalone",
+    "dev-tools/schema",
     # Do not include xtask in the list of default members, because this causes
     # hakari to not work as well and build times to be longer.
     # See omicron#4392.

Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "schema"
+version = "0.1.0"
+edition = "2021"
+license = "MPL-2.0"
+
+[lints]
+workspace = true
+
+[build-dependencies]
+omicron-rpaths.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+camino.workspace = true
+clap.workspace = true
+nexus-db-model.workspace = true
+omicron-workspace-hack.workspace = true
+pq-sys = "*"
+semver.workspace = true

dev-tools/schema/Cargo.toml

@@ -0,0 +1,10 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// See omicron-rpaths for documentation.
+// NOTE: This file MUST be kept in sync with the other build.rs files in this
+// repository.
+fn main() {
+    omicron_rpaths::configure_default_omicron_rpaths();
+}