Improve help outputs

[AllanOricil]

Do something like volta

Enhancements

actual

desired

• flags without a char should be formatted on the same column.
• remove =<value> after a flag.
• colorize (required) and [default: ...] with different colors.
• add the type of each flag right after the flag name like docker does.

other small changes

• the word (required) could be changed to *
• the word [default: value ...] could be just [value] since its "unit of measure" (minutes, for example) is already mentioned in the description

[AllanOricil]

@mshanemc this is also oclif scope right?

[AllanOricil]

I divided this enhancement into a few tasks:

• enable themes ✅
• improve flags renderer to:
  • display flags into 2 columns ✅
  • include flag type label ✅
  • remove "=<value>"✅
• create default theme for sf|sfdx cli
• enable users to create their custom themes using plugins

[AllanOricil]

The removal of =<value> was not accepted. The other stuff are pretty much done in the core package.