Userland+AK: Stop using getopt() for ArgsParser

This commit moves the implementation of getopt into AK, and converts its
API to understand and use StringView instead of char*.
Everything else is caught in the crossfire of making
Option::accept_value() take a StringView instead of a char const*.

With this, we must now pass a Span<StringView> to ArgsParser::parse(),
applications using LibMain are unaffected, but anything not using that
or taking its own argc/argv has to construct a Vector<StringView> for
this method.

Userland/Utilities/strings.cpp

@@ -108,8 +108,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         nullptr,
         't',
         "format",
-        [&string_offset_format](char const* s) {
-            StringView value = { s, strlen(s) };
+        [&string_offset_format](StringView value) {
             if (value == "d") {
                 string_offset_format = StringOffsetFormat::Decimal;
             } else if (value == "o") {