std: add writer methods on all crypto.hash types

[nektro]

This enables many use cases but the one piqued my interest in this is if you're hashing many files in sequence. since the hash types are able to take in a continuous stream of bytes through .update, one can setup a std.fifo.LinearFifo and hash the files' contents with zero allocations by doing try fifo.pump(file.reader(), hasher.writer());

[nektro]

adding this worked too

fn HashWriter(comptime T: type) type {
    return struct {
        h: *T,

        const Self = @This();
        pub const Error = error{};
        pub const Writer = std.io.Writer(*Self, Error, write);

        fn write(self: *Self, bytes: []const u8) Error!usize {
            self.h.update(bytes);
            return bytes.len;
        }

        pub fn writer(self: *Self) Writer {
            return .{ .context = self };
        }
    };
}

[jedisct1]

No love for Gimli and SipHash?

[nektro]

oh good catch, I thought I'd added those too