all: clean up code with Go 1.24+ in mind (#5489)

* all: clean up code with Go 1.24+ in mind

* all: more old go cleanup

* all: even remove rand_fastrand64

* runtime: revert rand changes

* runtime: re-drop rand_fastrand64

loader/loader.go

@@ -27,8 +27,6 @@ import (
 	"github.com/tinygo-org/tinygo/goenv"
 )
 
-var initFileVersions = func(info *types.Info) {}
-
 // Program holds all packages and some metadata about the program as a whole.
 type Program struct {
 	config      *compileopts.Config
@@ -435,7 +433,7 @@ func (p *Package) Check() error {
 		}
 		checker.GoVersion = fmt.Sprintf("go%d.%d", major, minor)
 	}
-	initFileVersions(&p.info)
+	p.info.FileVersions = make(map[*ast.File]string)
 
 	// Do typechecking of the package.
 	packageName := p.ImportPath

loader/loader_go122.go

@@ -1,17 +0,0 @@
-//go:build go1.22
-
-// types.Info.FileVersions was added in Go 1.22, so we can only initialize it
-// when built with Go 1.22.
-
-package loader
-
-import (
-	"go/ast"
-	"go/types"
-)
-
-func init() {
-	initFileVersions = func(info *types.Info) {
-		info.FileVersions = make(map[*ast.File]string)
-	}
-}