test: run integration tests on random ports and speed up slow tests (#39842)

Integration test processes now get their own work directory, config file
and random ports, so several runs can execute in parallel on one
machine. The slowest tests also lose fixed sleeps and needlessly
expensive setup, with their assertions kept.

- Batch PostgreSQL sequence resets, the main per-test fixture cost there
- Cheap hashing params in hash and OAuth2 fixture tests, full-cost
vectors stay
- Single fetch for negative Actions runner assertions instead of 1s
polls
- Queue flushes and backdated timestamps instead of sleeps
- In-memory SQLite test journal, tmpfs for PostgreSQL in CI
- E2E instance writes SSH keys into its work directory instead of
`~/.ssh/authorized_keys`

modules/indexer/issues/internal/tests/tests.go

@@ -8,6 +8,7 @@
 package tests
 
 import (
+	"context"
 	"fmt"
 	"slices"
 	"testing"
@@ -744,6 +745,9 @@ func countIndexerData(data map[int64]*internal.IndexerData, f func(v *internal.I
 // waitData waits for the indexer to index all data.
 // Some engines like Elasticsearch index data asynchronously, so we need to wait for a while.
 func waitData(t *testing.T, indexer internal.Indexer, total int64) {
+	if refresher, ok := indexer.(interface{ Refresh(context.Context) error }); ok {
+		require.NoError(t, refresher.Refresh(t.Context()))
+	}
 	assert.Eventually(t, func() bool {
 		result, err := indexer.Search(t.Context(), &internal.SearchOptions{Paginator: &db.ListOptions{}})
 		require.NoError(t, err)