Prevent Usage of Stdlib File/Dir Writing With Static Analysis (#7685)

* write file and mkdirall analyzers

* include analyzer in build bazel

* comments to the single entrypoint and fix validator references

* enforce 600 for files, 700 for dirs

* pass validator tests

* add to nogo

* remove references

* beaconfuzz

* docker img

* fix up kv issue

* mkdir if not exists

* radek comments

* final comments

* Try to fix file problem

Co-authored-by: Ivan Martinez <ivanthegreatdev@gmail.com>

tools/interop/export-genesis/BUILD.bazel

@@ -9,6 +9,7 @@ go_library(
     deps = [
         "//beacon-chain/cache:go_default_library",
         "//beacon-chain/db:go_default_library",
+        "//shared/fileutil:go_default_library",
     ],
 )
 

tools/interop/export-genesis/main.go

@@ -3,11 +3,11 @@ package main
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"os"
 
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db"
+	"github.com/prysmaticlabs/prysm/shared/fileutil"
 )
 
 // A basic tool to extract genesis.ssz from existing beaconchain.db.
@@ -41,7 +41,7 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
-	if err := ioutil.WriteFile(os.Args[2], b, 0644); err != nil {
+	if err := fileutil.WriteFile(os.Args[2], b); err != nil {
 		panic(err)
 	}
 	fmt.Println("done")