Implement sub form of &trans, mainly to support feed operators.

[gfldex]

Tests:

use v6.*;
use Test;

my @with-pair;
<abc bbc cbc> ==> trans('b' => 'B') ==> @with-pair;
is-deeply @with-pair, <aBc BBc cBc>.Array, 'trans with feed operator and pair';

my @with-positional;
<abc bbc cbc> ==> trans(['a' => 'A', 'c' => 'C']) ==> @with-positional;
is-deeply @with-positional, <AbC bbC CbC>.Array, 'trans with feed operator and Array';
@with-positional = ();
<abc bbc cbc> ==> trans(('a' => 'A', 'c' => 'C')) ==> @with-positional;
is-deeply @with-positional, <AbC bbC CbC>.Array, 'trans with feed operator and List';

my @with-flags;
<a111bc b222bc c333bc> ==> trans('a'..'z' => 'x', :complement, :squash) ==> @with-flags;
is-deeply @with-flags, ["axbc", "bxbc", "cxbc"], 'trans with feed operator and named flags';

[gfldex]

Updated Tests:

my @with-pair;
<abc bbc cbc> ==> trans('b' => 'B') ==> @with-pair;
is-deeply @with-pair, <aBc BBc cBc>.Array, 'trans with feed operator and pair';

my @with-positional;
<abc bbc cbc> ==> trans('a' => 'A', 'c' => 'C') ==> @with-positional;
is-deeply @with-positional, <AbC bbC CbC>.Array, 'trans with feed operator and many args';

my @with-flags;
<a111bc b222bc c333bc> ==> trans('a'..'z' => 'x', :complement, :squash) ==> @with-flags;
is-deeply @with-flags, ["axbc", "bxbc", "cxbc"], 'trans with feed operator and named flags';

is trans('a' => 'A', 'abc'), 'Abc', 'trans as function call and single Str';
is trans('a' => 'A', 'b' => 'B', 'abc'), 'ABc', 'trans as function call with multiple replacements and single Str';
is-deeply trans('a' => 'A', <abc bbc cbc>), <Abc bbc cbc>, 'trans as function call with Array of Str';