ROUTE53: Rewrite to use diff2

[tlimoncelli]

CC @tresni

It is roughly working! Now I just have to clean up the little stuff.

[tlimoncelli]

This is ready for review, @tresni !

It doesn't do batching (i.e. it sends 1 RPC per change) but it passes all tests. I'd like to merge this (pending any feedback) then come back later and add batching. (Or, not add batching? I dunno how important it is.)

[tresni]

R53's API limits are very low (5 requests per second). For mass operations, batching is basically a requirement.

Retries may alleviate this for some cases, but I'm not sure it would be a good strategy overall. (e.g. if you have 1000 records changing, without batching you are looking at ~5 minutes to process all changes, vs a potential single request with batching.)

[tlimoncelli]

ok, good point!

I've added batching support. Time went from 1m35s to 1m25s. However if I include the tests like 601 and 1201 the time goes from 20m to 1.5. A huge improvement!

It was extremely easy to add batched support because of the existing batcher support. According to git blame, I that was added by @jtdoepke. Thanks!

This is ready for review. Lemme know what you think!