backport: performance improvements for the event query API (#7319) (#9334)

* Performance improvements for the event query API (#7319)

Rework the implementation of event query parsing and execution to
improve performance and reduce memory usage.

Previous memory and CPU profiles of the pubsub service showed query
processing as a significant hotspot. While we don't have evidence that
this is visibly hurting users, fixing it is fairly easy and self-contained.

Updates #6439.

Typical benchmark results comparing the original implementation (PEG) with the reworked implementation (Custom):
```
TEST                        TIME/OP  BYTES/OP  ALLOCS/OP  SPEEDUP   MEM SAVING
BenchmarkParsePEG-12       51716 ns  526832    27
BenchmarkParseCustom-12     2167 ns    4616    17         23.8x     99.1%
BenchmarkMatchPEG-12        3086 ns    1097    22
BenchmarkMatchCustom-12    294.2 ns      64     3         10.5x     94.1%
```

libs/pubsub/query/oldquery/empty_test.go

@@ -0,0 +1,28 @@
+package query_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	query "github.com/tendermint/tendermint/libs/pubsub/query/oldquery"
+)
+
+func TestEmptyQueryMatchesAnything(t *testing.T) {
+	q := query.Empty{}
+
+	testCases := []struct {
+		query map[string][]string
+	}{
+		{map[string][]string{}},
+		{map[string][]string{"Asher": {"Roth"}}},
+		{map[string][]string{"Route": {"66"}}},
+		{map[string][]string{"Route": {"66"}, "Billy": {"Blue"}}},
+	}
+
+	for _, tc := range testCases {
+		match, err := q.Matches(tc.query)
+		assert.Nil(t, err)
+		assert.True(t, match)
+	}
+}