<!--Describe the documentation added.-->
#### Documentation
Creates an internal architecture file. In it is a diagram of the startup
flow of the collector as well as links to key files / packages. I also
added package level comments to some key packages.
I wrote some other documentation in
https://github.com/open-telemetry/opentelemetry-collector/pull/10029 but
split the PRs up.
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Co-authored-by: Pablo Baeyens <pbaeyens31+github@gmail.com>
Ankit Patel