Support tailing files created after startup in tail input.

[danielnelson]

Feature Request

Proposal:

Logparser supports tailing new files that match the list of patterns as they are created. Before we can deprecate the logparser plugin we need to add this functionality to the tail input. Also update the github label to be area/tail.

Current behavior:

The tail plugin checks for matching files on startup only.

Desired behavior:

Check for new matches dynamically.