util: support 128 FastIntSet elements without allocation

This commit increases the size of the "small set" bitmap from 64 bits
to 128 bits. The main goal is to avoid the slow path in optimizer
ColSets for more queries.

Fixes #72733.

Release note: None

pkg/ccl/logictestccl/testdata/logic_test/as_of

@@ -174,7 +174,7 @@ SELECT * FROM t AS OF SYSTEM TIME with_max_staleness('1ms') WHERE j = 2
 query T
 EXPLAIN (OPT, MEMO) SELECT * FROM t AS OF SYSTEM TIME with_max_staleness('1ms') WHERE j = 2 AND i = 1
 ----
-memo (optimized, ~7KB, required=[presentation: info:6])
+memo (optimized, ~8KB, required=[presentation: info:6])
  ├── G1: (explain G2 [presentation: i:1,j:2,k:3])
  │    └── [presentation: info:6]
  │         ├── best: (explain G2="[presentation: i:1,j:2,k:3]" [presentation: i:1,j:2,k:3])

pkg/sql/opt/exec/execbuilder/testdata/explain

@@ -1594,7 +1594,7 @@ regions: <hidden>
 query T
 EXPLAIN (OPT, MEMO) SELECT * FROM tc JOIN t ON k=a
 ----
-memo (optimized, ~14KB, required=[presentation: info:10])
+memo (optimized, ~16KB, required=[presentation: info:10])
  ├── G1: (explain G2 [presentation: a:1,b:2,k:6,v:7])
  │    └── [presentation: info:10]
  │         ├── best: (explain G2="[presentation: a:1,b:2,k:6,v:7]" [presentation: a:1,b:2,k:6,v:7])
@@ -1653,7 +1653,7 @@ TABLE t
  ├── tableoid oid [hidden] [system]
  └── PRIMARY INDEX t_pkey
       └── k int not null
-memo (optimized, ~14KB, required=[presentation: info:10])
+memo (optimized, ~16KB, required=[presentation: info:10])
  ├── G1: (explain G2 [presentation: a:1,b:2,k:6,v:7])
  │    └── [presentation: info:10]
  │         ├── best: (explain G2="[presentation: a:1,b:2,k:6,v:7]" [presentation: a:1,b:2,k:6,v:7])

pkg/sql/opt/exec/explain/plan_gist_factory.go

@@ -39,11 +39,15 @@ func init() {
 	}
 }
 
-// version tracks major changes to how we encode plans or to the operator set.
-// It isn't necessary to increment it when adding a single operator but if we
-// remove an operator or change the operator set or decide to use a more
+// gistVersion tracks major changes to how we encode plans or to the operator
+// set. It isn't necessary to increment it when adding a single operator but if
+// we remove an operator or change the operator set or decide to use a more
 // efficient encoding version should be incremented.
-var version = 1
+//
+// Version history:
+//   1. Initial version.
+//   2. FastIntSet encoding changed.
+var gistVersion = 2
 
 // PlanGist is a compact representation of a logical plan meant to be used as
 // a key and log for different plans used to implement a particular query. A
@@ -117,7 +121,7 @@ func NewPlanGistFactory(wrappedFactory exec.Factory) *PlanGistFactory {
 	f := new(PlanGistFactory)
 	f.wrappedFactory = wrappedFactory
 	f.hash.Init()
-	f.encodeInt(version)
+	f.encodeInt(gistVersion)
 	return f
 }
 
@@ -186,8 +190,8 @@ func DecodePlanGistToPlan(s string, cat cat.Catalog) (plan *Plan, retErr error)
 	}()
 
 	ver := f.decodeInt()
-	if ver != version {
-		return nil, errors.Errorf("unsupported old plan gist version %d", ver)
+	if ver != gistVersion {
+		return nil, errors.Errorf("unsupported gist version %d (expected %d)", ver, gistVersion)
 	}
 
 	for {