refactor SubtleCrypto

I've been thinking the implementation here is messy (ever since we added support for it) and thought it would be better to separate each algorithm to their respective files in order to maintain in a long run. `digest` is also refactored to prefer libcrypto instead of std.

src/network/WebBotAuth.zig

@@ -17,7 +17,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const crypto = @import("../crypto.zig");
+const crypto = @import("../sys/libcrypto.zig");
 
 const Http = @import("../network/http.zig");