Support configurable tagging of AWS resources created by the agent

**Is your feature request related to a problem? Please describe.**
The Cloudwatch Agent creates Cloudwatch Log Groups to push logs to for analysis. We use tags internally for tracking ownership and cost allocation and the agent currently doesn't support being configured to tag the log groups created.

**Describe the solution you'd like**
Allowing users to configure the agent to tag the Cloudwatch Log Groups created with user specified KV pairs.

**Describe alternatives you've considered**
Manual tagging of the log groups post creation - this isn't very scalable.

**Additional context**
None

The issue names CloudWatch Log Groups created by the agent but no files or tests. Start by locating the agent's log-group creation path and configuration parsing, then trace how user-specified key/value tags could reach that call; done means configured tags are applied to newly created groups and the behavior is covered by the relevant tests.

Written by the indexing model from the issue text.