allowing c3c test -- <args1>

[alexveden]

A small improvement for #1774

Allowing custom and default test/bench runners receiving arguments:

fn bool default_test_runner(String[] args)
{
	io::printfn("default_test_runner: %s", args);
	return false;
}

> c3c test --testfn "std::core::test::default_test_runner" -- foo --bar

Program linked to executable 'build/testrun'.
Launching ./build/testrun foo --bar
default_test_runner: [./build/testrun, foo, --bar]

The same behavior is consistent when we do direct run of compiled test runner:

> ./build/testrun foo --bar

default_test_runner: [./build/testrun, foo, --bar]

We might be getting help via:

c3c test -- --help

This will decouple @tests/@benchmark runner logic completely from c3c compiler space into c3 (stdlib space) or custom runner space.

[alexveden]

A show case how it can work:

~/code/c3test ➜ c3c test --testfn "std::core::test::default_test_runner" -- --help

Program linked to executable 'build/testrun'.
Launching ./build/testrun --help

Usage:
testrun [options]

c3c default test runner

Test options
    -h, --help            show this help message and exit
    -f, --filter=<str>    filter tests by name, e.g. some::test, or some [default: ]
    -b, --breakpoint      emits breakpoint if any assert() is failed [default: false]
    --sort                sort all tests alphabetically by name, --no-sort - preserve natural order [default: true]
    -c, --color           test output with colors [default: false]
Program completed with exit code 1.