XS for Int is faster inline

[zmughal]

As discussed on Mastodon,
this was determined using the following script:

#!/usr/bin/env perl

use Benchmark qw(cmpthese);
use Type::Tiny::XS;

print "$^V\n";
cmpthese(50_000_000, {
	regex => sub { my $my_val = '1000000'; die unless do { my $tmp = $my_val; defined($tmp) and !ref($tmp) and $tmp =~ /\A-?[0-9]+\z/ }  },
	xs    => sub { my $my_val = '1000000'; die unless Type::Tiny::XS::Int($my_val)  },
});
__END__
v5.38.0
            Rate regex    xs
regex  3351206/s    --  -76%
xs    14044944/s  319%    --

[zmughal]

Hello @tobyink, bumping this PR in case you have a tuit.