Implement ChaCha20 Crypto in stdlib (#2643)

* ChaCha20 implementation, first pass

* fix bug with clone_slice when length is 0

* final ChaCha20 crypto tidying

* final adjustments; add benchmark

* add guards everywhere else or w/e

* stdlib 'i++' conformity

* release notes & security warning updates

* update tests; cleanup; default counter should be 0 not 1

* remove prints in test file

* add extra unit tests for unaligned buffers

Co-authored-by: Manu Linares <mbarriolinares@gmail.com>

* one final alignment test

* nice contraction of tests w/ some paranoia sprinkled in

* nearly double the efficiency of chacha20's transform

Co-authored-by: Manu Linares <mbarriolinares@gmail.com>

* fix memory leak in test case

* improve one of the unit tests to cover more cases

* greatly simplify chacha20 'transform'

Co-authored-by: Manu Linares <mbarriolinares@gmail.com>

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Co-authored-by: Manu Linares <mbarriolinares@gmail.com>

lib/std/core/mem_allocator.c3

@@ -326,6 +326,8 @@ macro clone(Allocator allocator, value) @nodiscard
 *>
 macro clone_slice(Allocator allocator, slice) @nodiscard
 {
+	if (!lengthof(slice)) return {};
+
 	var $Type = $typeof(slice[0]);
 
 	$Type[] new_arr = new_array(allocator, $Type, slice.len);