chloggen: add support for grouping changes by component

[axw]

Users don't necessarily care about changes to all components in a changelog. For example, users of the contrib collector are likely to use only a handful of receivers and exporters, rather than all of them.

To avoid users having to search through the changelog for entries relevant to them, it would be helpful to group changes by component.

See open-telemetry/opentelemetry-collector-contrib#40593