There should be a consolidated package for configuration validations

[SaxyPandaBear]

As observed in #418, there looks like a gap in how the agent uses/validates configurations. We either ignore a code path or are forced to duplicate validation code across packages for different executables. For example, we may expect some semantic validation to be done in the config-translator, but don't double confirm the value is correct in the main agent executable, amazon-cloudwatch-agent.

It would be a pretty beefy change, but I think what we could add is a validation package (I'm bad at naming, so not married to this name in particular) which would exist as a utility package that acts as a single source of validations that we can reference in any of the other executables. It feels like bad design and coupling to write validation in something like the translator package, but then expect to use it in something that isn't doing any translation (the agent would be using the output of the translation, though).

[SaxyPandaBear]

Closing out since we're sticking to not supporting customer modified TOML