Support for S3 caching

[prashcr]

Cody supports local cache, but I've found it quite pointless as the cache hits are extremely conditional on a number of factors.

https://stackoverflow.com/a/59070807/4131237

Not from any public source, but these are some observations:

The cache will only be available if the build time is more than 5 minutes.

* Cache can be used if the new build is successfully placed on the same build host.

* Cache can be used if the new build is being run within 5-15 minutes of the last build. Cache may stay available based on the last build time with a max of 15 minutes.

* Despite builds exceeding 5 minutes, the cache may not always work probably due to build being placed on different build host.

* Additionally, in the case where the cache speeds up the new build to below 5 minutes, that build will not be cached resulting in subsequent miss.

It'd be great to allow configuring S3 cache with Cody by specifying the bucket name.

[tongueroo]

Believe that Cody already allow using s3 as a cache by using the cache method and setting the properties directly. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-codebuild-project-projectcache.html

A s3_cache convenience method would be nice though. Will consider PRs. No sweat either way though, will get to it in time.