Meta+Userland: Simplify some formatters

These are mostly minor mistakes I've encountered while working on the
removal of StringView(char const*). The usage of builder.put_string over
Format<FormatString>::format is preferrable as it will avoid the
indirection altogether when there's no formatting to be done. Similarly,
there is no need to do format(builder, "{}", number) when
builder.put_u64(number) works equally well.

Additionally a few Strings where only constant strings were used are
replaced with StringViews.

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -375,7 +375,7 @@ bool UnsignedBigInteger::operator>=(UnsignedBigInteger const& other) const
 ErrorOr<void> AK::Formatter<Crypto::UnsignedBigInteger>::format(FormatBuilder& fmtbuilder, Crypto::UnsignedBigInteger const& value)
 {
     if (value.is_invalid())
-        return Formatter<StringView>::format(fmtbuilder, "invalid");
+        return fmtbuilder.put_string("invalid"sv);
 
     StringBuilder builder;
     for (int i = value.length() - 1; i >= 0; --i)