Interpolate tags in the AWS S3 sink

[bruceg]

The AWS S3 sink has now added the ability to specify tags (introduced in PR #1689). These tags do not support interpolation of values, either from event data or from the environment. Support for full interpolation should be added to allow for dynamic values.

[enzo-arefi]

Dynamic tag values would allow for dynamic lifecycle handling on the AWS side, for example.

[RacekM]

Another use case would be the possibility of defining policies in s3 according to the tagged values.

For example, we could define a policy that would grant users access to all log files with the tag "DNS". All syslog messages with an 'app_name=dns' would be accessible to all users with the mentioned policy.