Add systemd receiver to manifest.yaml

[khushijain21]

Add systemd receiver to manifest.yaml of otel contrib collector

[glimchb]

@khushijain21 can you please do the same for redfish receiver ? #1271

[crobert-1]

The component is marked as development stability, which means it's likely not intended to be in the distribution yet. The usual process is to mark it as alpha and then include it in the contrib distribution. Please review the Adding New Components documentation for more information on new components being added to the disitribution.

Please reach out to code owners in contrib before introducing this component to a released distribution.