Breaking: sort std/crypto functions into categories

Instead of having all primitives and constructions share the same namespace,
they are now organized by category and function family.

Types within the same category are expected to share the exact same API.

tools/process_headers.zig

@@ -313,7 +313,7 @@ pub fn main() !void {
     var max_bytes_saved: usize = 0;
     var total_bytes: usize = 0;
 
-    var hasher = std.crypto.Sha256.init();
+    var hasher = std.crypto.hash.sha2.Sha256.init();
 
     for (libc_targets) |libc_target| {
         const dest_target = DestTarget{