Restructure packages from current "service" package

[bogdandrutu]

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This is a proposal to restructure current large "service" package with multiple dependencies, and too many features to match the configuration "service" part:

• [ ] Will create a package under "service" directory for every config service subcomponent (telemetry, pipelines, extensions). These packages will follow the format:
  • Config struct for configuration, similar to all other components.
  • Will not use a "Factory" since I don't think we want necessary to allow this to be pluginable, but will offer an API like New(context.Context, Settings) or Build(context.Context, Settings).
• [ ] Telemetry initialization logic will be moved into this package service/telemetry.go file.
• [ ] The current service package will become the package that implements the current service part of the config. Which means also will implement the "Host" interface. This package will have a Config which will represent the current "service::" configuration.
• [ ] Create a new "collector" package and move the current "Collector", "windows.SvcHandler", "Command", "ConfigProvider" structs and related constructors/helpers.
  • Things related to flags will also be moved there.
• [ ] service/featuregate will be moved as a top directory featuregate.

Advantages:

1. Better match of the features/structure with the configuration structure.
2. Allow external parties to use a "sub-component" of the collector (telemetry, extensions, etc.). This will fix https://github.com/open-telemetry/opentelemetry-collector/issues/4970