all: merge master (e65ea15) into gopls-release-branch.0.18

Also add back the x/tools replace directive.

For golang/go#71607

Merge List:

+ 2025-02-07 e65ea15 go/analysis/internal/checker: implement three-way merge
+ 2025-02-07 a9bf6fd gopls/internal/analysis/modernize: remove SortStable
+ 2025-02-07 4d1de70 internal/apidiff: remove

Change-Id: I85447333201cddcc9f0aa8ba711af28abdc877c7

Author: findleyr

go/analysis/analysistest/analysistest.go

@@ -36,6 +36,12 @@ import (
 // and populates it with a GOPATH-style project using filemap (which
 // maps file names to contents). On success it returns the name of the
 // directory and a cleanup function to delete it.
+//
+// TODO(adonovan): provide a newer version that accepts a testing.T,
+// calls T.TempDir, and calls T.Fatal on any error, avoiding the need
+// to return cleanup or err:
+//
+//	func WriteFilesToTmp(t *testing.T filemap map[string]string) string
 func WriteFiles(filemap map[string]string) (dir string, cleanup func(), err error) {
 	gopath, err := os.MkdirTemp("", "analysistest")
 	if err != nil {