feat: add flagSortOrder to help options

[mdonnalley]

Adds flagSortOrder to helpOptions

Two options:

• alphabetical: Sort flags alphabetically. All flags with short characters will come first. (Default behavior)
• none: Do not sort flags. They will appear in the order in which they were defined on the command.

To use, add flagSortOrder to helpOptions in your CLI's package.json

"oclif": {
  "helpOptions": {
    "flagSortOrder": "none"
  }
}

Fixes oclif/oclif#1214

@W-14626665@

[cristiand391]

QA notes:

✅ no option defined, defaults to sorted
✅ oclif.helpOptions.flagSortOrder = none, unsorted
✅ oclif.helpOptions.flagSortOrder = none, sorted

🟡 sort order option isn't validated at runtime:
while in TS only alphabetical or none is supported, this config is read from json so any typos make it render flags as unsorted.

do you think it's worth validating this at runtime? not sure it should throw or warn (also don't know if oclif validates any psjon settings).