*: remove uses of reflect.MethodByName from all of Delve (#3916)

When reflect.MethodByName is used the linker can not fully perform
deadcode elimination. This commit updates cobra and rewrites the
suitableMethods part of service/rpccommon so that reflect.MethodByName
is not used and the linker can fully execute deadcode elimination.

The executable size on go1.24.0 on linux is reduced from 25468606 bytes
to 22453382 bytes or a reduction of approximately 12%.

See also:

https://github.com/spf13/cobra/pull/1956
https://github.com/aarzilli/whydeadcode

_scripts/gen-suitablemethods.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"go/token"
+	"go/types"
+	"io"
+	"log"
+	"os"
+	"strings"
+
+	"golang.org/x/tools/go/packages"
+)
+
+func must(err error, fmtstr string, args ...interface{}) {
+	if err != nil {
+		log.Fatalf(fmtstr, args...)
+	}
+}
+
+func main() {
+	buf := bytes.NewBuffer([]byte{})
+	fmt.Fprintf(buf, "// DO NOT EDIT: auto-generated using _scripts/gen-suitablemethods.go\n\n")
+	fmt.Fprintf(buf, "package rpccommon\n\n")
+	fmt.Fprintf(buf, "import ( \"reflect\"; \"github.com/go-delve/delve/service/rpc2\" )\n")
+
+	dorpc(buf, "rpc2.RPCServer", "rpc2", "2")
+	dorpc(buf, "RPCServer", "rpccommon", "Common")
+
+	src, err := format.Source(buf.Bytes())
+	must(err, "error formatting source: %v", err)
+
+	out := os.Stdout
+	if os.Args[1] != "-" {
+		if !strings.HasSuffix(os.Args[1], ".go") {
+			os.Args[1] += ".go"
+		}
+		out, err = os.Create(os.Args[1])
+		must(err, "error creating %s: %v", os.Args[1], err)
+	}
+	_, err = out.Write(src)
+	must(err, "error writing output: %v", err)
+	if out != os.Stdout {
+		must(out.Close(), "error closing %s: %v", os.Args[1], err)
+	}
+}
+
+func dorpc(buf io.Writer, typename, pkgname, outname string) {
+	fmt.Fprintf(buf, "func suitableMethods%s(s *%s, methods map[string]*methodType) {\n", outname, typename)
+
+	fset := &token.FileSet{}
+	cfg := &packages.Config{
+		Mode: packages.NeedSyntax | packages.NeedTypesInfo | packages.NeedName | packages.NeedCompiledGoFiles | packages.NeedTypes,
+		Fset: fset,
+	}
+	pkgs, err := packages.Load(cfg, fmt.Sprintf("github.com/go-delve/delve/service/%s", pkgname))
+	must(err, "error loading packages: %v", err)
+	packages.Visit(pkgs, func(pkg *packages.Package) bool {
+		if pkg.PkgPath != fmt.Sprintf("github.com/go-delve/delve/service/%s", pkgname) {
+			return true
+		}
+		mset := types.NewMethodSet(types.NewPointer(pkg.Types.Scope().Lookup("RPCServer").Type()))
+		for i := 0; i < mset.Len(); i++ {
+			fn := mset.At(i).Obj().(*types.Func)
+			name := fn.Name()
+			if name[0] >= 'a' && name[0] <= 'z' {
+				continue
+			}
+			sig := fn.Type().(*types.Signature)
+			if sig.Params().Len() != 2 {
+				continue
+			}
+			fmt.Fprintf(buf, "methods[\"RPCServer.%s\"] = &methodType{ method: reflect.ValueOf(s.%s) }\n", name, name)
+
+		}
+		return true
+	}, nil)
+	fmt.Fprintf(buf, "}\n\n")
+}