Target Allocator Support for Native Prometheus Receiver

[okankoAMZ]

Description of the issue

We have a new tool called Target Allocator, which provides scrape configs. These changes allows telegraf based prometheus receiver to pull scrape configs from Target Allocator endpoint.

There was a bug on config returning if TA exist instead of does not exist on this PR(#1390) thus reverted and created this one.

Description of changes

• Added Target Allocator Manager(TAM), based on contrib version but with a wrapper
• TAM is now included and checked during initial and reload configs to make sure TA is enabled or disabled.
• When TA is enabled the TAM will provide the prometheus config to telegraf prometheus receiver directly. (without a file read)

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

• Added some unit tests which pass
• Manually tested where I can see metrics on CloudWatch when Agent is deployed.

Requirements

Before commit the code, please do the following steps.

1. Run make fmt and make fmt-sh
2. Run make lint

[musa-asad]

Fixed my nits so that the asked change is clear.

[sky333999]

Approving from prior reviews