Fix cli package from mangling option arguments with equal signs

[ergl]

The current command parser in the cli package cuts option arguments of String type at the first equal sign. This release fixes the problem for long options (--option=foo=bar) and for short options such as -O=foo=bar. Short options such as -Ofoo=bar will continue to raise an "ambiguous args" error.

The code below shows the bug, with the option argument being cut short at the first equal sign. The code below prints "foo" instead of the complete value, "foo=bar". The same is true when uses the short version of the option, like -t=foo=bar.

use "cli"

actor Main
  new create(env: Env) =>
    try
      let cs =
        CommandSpec.leaf("simple", "", [
          OptionSpec.string("test" where short' = 't')
        ])?
      
      let args: Array[String] = [
        "ignored"; "--test=foo=bar"
      ]
      let cmdErr = CommandParser(cs).parse(args) as Command
      env.out.print(cmdErr.option("test").string())
    end

[ergl]

Fixed a repeated test name as I went along.