(feat) specify root repo path using DEV_REPO_ROOT for debugging

[alexandreLamarre]

• Allows specifying relative/absolute root repo paths for debugging by developers

• correctly pass in configuration.yaml path config flag : places where defaultChartsScriptOptionsFile were used should've been using ChartsScriptOptionsFile instead

configFlag := cli.StringFlag{
		Name:        "config",
		Usage:       "A configuration file with additional options for allowing this branch to interact with other branches",
		TakesFile:   true,
		Destination: &ChartsScriptOptionsFile,
		Value:       defaultChartsScriptOptionsFile,
	}

• Migrated references of deprecated ioutil package to stable:
  • ioutil.ReadFile -> os.Readfile
  • ioutil.WriteFile -> os.WriteFile
  • ioutil.MkdirTemp -> os.Mkdirtemp

[alexandreLamarre]

One of the main reasons, I've removed os.Getwd() definitions in package functions is to get rid of scenarios where all functions are not sharing the same abstraction for the repoRoot -- in the case where we make changes like this one.

In this PR I'm preferring using getRepoRoot() function defined in main.go and passing it through to sub functions as that seemed to be mostly the standard when Arvind was still working on the project

[alexandreLamarre]

We could also have a shared variable in pkg/charts, along the lines of:

func init() {

  repoRoot, err := os.Getwd()
  if err != nil {
    logrus.Fatal(err)
  } 
  DefaultRepoRoot= repoRoot
}

var (
  // default value
  DefaultRepoRoot = ""
  // flag writes to this one
  RepoRoot = ""
)

which could get passed in / written to as a cli.Flag, and consumers would use as charts.RepoRoot, but I opted for simplicity here

[alexandreLamarre]

Could alternatively pass in just the repoRoot string and construct the billy.Filesystem inside this function to avoid duplicate parameters in function signatures, although I was unsure if the workDir should ALWAYS be the repoRoot in the autobumps/lifecycle code

[alexandreLamarre]

Note this also allows for embedding git submodules which would be useful for integration tests in testify, which I think would both greatly reduce the amount of bugs shipped to charts-build-scripts, but also increase iteration speed