checklocks: make behavior configurable.

Defaults are the same, but certain behaviors can now be disabled to more easily
use the analyzer on its own. Now wrappers, lock inferrence and atomic default
analysis can be disabled. For example:

```
go vet -vettool=$HOME/go/bin/checklocks -wrappers=false -inferred=false -atomic=false ./...
```

Fixes #7721

PiperOrigin-RevId: 455393957

tools/checklocks/analysis.go

@@ -268,6 +268,10 @@ func (pc *passContext) checkGuards(inst almostInst, from ssa.Value, accessObj ty
 			pc.maybeFail(inst.Pos(), "non-atomic write of field %s, writes must still be atomic with locks held (locks: %s)", accessObj.Name(), ls.String())
 		}
 	case atomicDisallow:
+		// If atomic analysis is not enabled, skip.
+		if !enableAtomic {
+			break
+		}
 		// Check that this is *not* used atomically.
 		if refs := inst.Referrers(); refs != nil {
 			for _, otherInst := range *refs {

tools/checklocks/annotations.go

@@ -91,6 +91,9 @@ func (pc *passContext) maybeFail(pos token.Pos, fmtStr string, args ...interface
 	if _, ok := pc.exemptions[pc.positionKey(pos)]; ok {
 		return // Ignored, not counted.
 	}
+	if !enableWrappers && !pos.IsValid() {
+		return // Ignored, implicit.
+	}
 	pc.pass.Reportf(pos, fmtStr, args...)
 }
 

tools/checklocks/checklocks.go

@@ -41,6 +41,18 @@ var Analyzer = &analysis.Analyzer{
 	},
 }
 
+var (
+	enableInferred = true
+	enableAtomic   = true
+	enableWrappers = true
+)
+
+func init() {
+	Analyzer.Flags.BoolVar(&enableInferred, "inferred", true, "enable inferred locks")
+	Analyzer.Flags.BoolVar(&enableAtomic, "atomic", true, "enable atomic checks")
+	Analyzer.Flags.BoolVar(&enableWrappers, "wrappers", true, "enable analysis of wrappers")
+}
+
 // objectObservations tracks lock correlations.
 type objectObservations struct {
 	counts map[types.Object]int
@@ -187,7 +199,9 @@ func run(pass *analysis.Pass) (interface{}, error) {
 	}
 
 	// Check for inferred checklocks annotations.
-	pc.checkInferred()
+	if enableInferred {
+		pc.checkInferred()
+	}
 
 	// Check for expected failures.
 	pc.checkFailures()