Shell: rewrite the whole shell to use tokens instead of raw strings

tab completion is still running with raw strings and that has to be
fixed in the future.

userspace/programs/Shell/Alias.cpp

@@ -0,0 +1,34 @@
+#include "Alias.h"
+
+BAN::ErrorOr<void> Alias::set_alias(BAN::StringView name, BAN::StringView value)
+{
+	TRY(m_aliases.insert_or_assign(
+		TRY(BAN::String::formatted("{}", name)),
+		TRY(BAN::String::formatted("{}", value))
+	));
+	return {};
+}
+
+BAN::Optional<BAN::StringView> Alias::get_alias(const BAN::String& name) const
+{
+	auto it = m_aliases.find(name);
+	if (it == m_aliases.end())
+		return {};
+	return it->value.sv();
+}
+
+
+void Alias::for_each_alias(BAN::Function<BAN::Iteration(BAN::StringView, BAN::StringView)> callback) const
+{
+	for (const auto& [name, value] : m_aliases)
+	{
+		switch (callback(name.sv(), value.sv()))
+		{
+			case BAN::Iteration::Break:
+				break;
+			case BAN::Iteration::Continue:
+				continue;;
+		}
+		break;
+	}
+}