build: improve cross compilation setup (#22804)

This PR cleans up the CI build system and fixes a couple of issues.

- The go tool launcher code has been moved to internal/build. With the new
  toolchain functions, the environment of the host Go (i.e. the one that built
  ci.go) and the target Go (i.e. the toolchain downloaded by -dlgo) are isolated
  more strictly. This is important to make cross compilation and -dlgo work
  correctly in more cases.
- The -dlgo option now skips the download and uses the host Go if the running Go
  version matches dlgoVersion exactly.
- The 'test' command now supports -dlgo, -cc and -arch. Running unit tests with
  foreign GOARCH is occasionally useful. For example, it can be used to run
  32-bit tests on Windows. It can also be used to run darwin/amd64 tests on
  darwin/arm64 using Rosetta 2.
- The 'aar', 'xcode' and 'xgo' commands now use a slightly different method to
  install external tools. They previously used `go get`, but this comes with the
  annoying side effect of modifying go.mod. They now use `go install` instead,
  which is the recommended way of installing tools without modifying the local
  module.
- The old build warning about outdated Go version has been removed because we're
  much better at keeping backwards compatibility now.

Makefile

@@ -26,7 +26,7 @@ android:
 	@echo "Import \"$(GOBIN)/geth.aar\" to use the library."
 	@echo "Import \"$(GOBIN)/geth-sources.jar\" to add javadocs"
 	@echo "For more info see https://stackoverflow.com/questions/20994336/android-studio-how-to-attach-javadoc"
-	
+
 ios:
 	$(GORUN) build/ci.go xcode --local
 	@echo "Done building."
@@ -46,12 +46,11 @@ clean:
 # You need to put $GOBIN (or $GOPATH/bin) in your PATH to use 'go generate'.
 
 devtools:
-	env GOBIN= go get -u golang.org/x/tools/cmd/stringer
-	env GOBIN= go get -u github.com/kevinburke/go-bindata/go-bindata
-	env GOBIN= go get -u github.com/fjl/gencodec
-	env GOBIN= go get -u github.com/golang/protobuf/protoc-gen-go
+	env GOBIN= go install golang.org/x/tools/cmd/stringer@latest
+	env GOBIN= go install github.com/kevinburke/go-bindata/go-bindata@latest
+	env GOBIN= go install github.com/fjl/gencodec@latest
+	env GOBIN= go install github.com/golang/protobuf/protoc-gen-go@latest
 	env GOBIN= go install ./cmd/abigen
-	@type "npm" 2> /dev/null || echo 'Please install node.js and npm'
 	@type "solc" 2> /dev/null || echo 'Please install solc'
 	@type "protoc" 2> /dev/null || echo 'Please install protoc'