Completes move fro Cool to Str

Leaving in Cool what it actually does, defer to Str. Closes #2303, if anyone has got any objection, please reopen and explain.

Author: JJ

doc/Type/Cool.pod6

@@ -1201,27 +1201,13 @@ L<Regex|/type/Regex> as a list of strings.
 
 =head2 method contains
 
-    multi method contains(Cool:D: Str(Cool) $needle, Cool $start? --> Bool:D)
-
-Coerces the invocant and first argument to L<C<Str>|/type/Str>, and
-searches for C<$needle> in the string starting from C<$start> characters
-into the string. Returns C<True> if C<$needle> is found. C<$start> is an
-optional parameter, and if it's not present, C<contains> will search
-from the beginning of the string.
-
-    say "Hello, World".contains('Hello');      # OUTPUT: «True␤»
-    say "Hello, World".contains('hello');      # OUTPUT: «False␤»
-    say "Hello, World".contains('Hello', 1);   # OUTPUT: «False␤»
-    say "Hello, World".contains(',');          # OUTPUT: «True␤»
-    say "Hello, World".contains(',', 3);       # OUTPUT: «True␤»
-    say "Hello, World".contains(',', 10);      # OUTPUT: «False␤»
-
-In the third case, the C<'Hello'> string is not found since we have
-started looking at the second position in it (index 1). Note that
-because of how a L<List|/type/List> or L<Array|/type/Array> is
-L<coerced|/type/List#method_Str> into a L<Str|/type/Str>, the results
-may sometimes be surprising. See
-L<traps|/language/traps#Lists_become_strings,_so_beware_.contains()>.
+Defined as:
+
+    method contains(Cool:D: |c)
+
+Coerces the invocant L<C<Str>|/type/Str>, and call
+L<C<Str.contains>|/type/Str#routine_contains> on it. Please refer to it
+for arguments and general syntax.
 
 =head2 routine index
 
@@ -1230,12 +1216,13 @@ Defined as:
     multi sub    index(Str(Cool) $s, Str:D $needle, Int(Cool) $startpos = 0 --> Int)
     multi method index(Str(Cool) $needle, Int(Cool) $startpos = 0 --> Int)
 
-Coerces the first two arguments (in method form, also counting the invocant)
-to L<Str|/type/Str>, and searches for C<$needle> in the string starting from C<$startpos>.
-It returns the offset into the string where C<$needle> was found, and an undefined
-value if it was not found.
+Coerces the first two arguments (in method form, also counting the
+invocant) to L<Str|/type/Str>, and searches for C<$needle> in the string
+starting from C<$startpos>. It returns the offset into the string where
+C<$needle> was found, and an undefined value if it was not found.
 
-See L<the documentation in type Str|/type/Str#routine_index> for examples.
+See L<the documentation in type Str|/type/Str#routine_index> for
+examples.
 
 =head2 routine rindex