[podmanreceiver] add scraper's shutdown method

[rogercoll]

Description:

• Adds the shutdown scraper method. The implementation cancels the containerEventLoop go routine. Similar to the dockerstats: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/dockerstatsreceiver/receiver.go#L76
• Moves the configuration validation to the start method, in alignment with the dockerstats receiver: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/dockerstatsreceiver/receiver.go#L55

Link to tracking Issue: Related issue #29994

Testing:
Use scraper instead of metrics receiver interface.

Documentation:

[rogercoll]

No changes on the end user, skip changelog?

[crobert-1]

I think since shutdown wasn't being called properly before (and we were leaking a goroutine), this can be considered a bug fix, so we probably want a changelog.

[crobert-1]

CI/CD failure:

Error: ../../receiver/podmanreceiver/factory.go:54:10: assignment mismatch: 1 variable but newMetricsReceiver returns 2 values
Error: ../../receiver/podmanreceiver/factory.go:54:51: not enough arguments in call to newMetricsReceiver
	have (receiver.CreateSettings, *Config, nil)
	want (context.Context, receiver.CreateSettings, *Config, consumer.Metrics, any)
make: *** [Makefile:[32](https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/9033747495/job/24824836747?pr=32981#step:7:33)7: otelcontribcol] Error 1

[crobert-1]

Thanks for fixing!

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: rogercoll / name: Roger Coll (6c4d2e5, 9a82696, 2bf6a4a, 1b6095d, 18d216c, 5bdfd32, 6b568e2, c00c4a5, 4e6da95, 08397a8, 31624bb, 50419a1, 21a0e55, 863440d, e86e8c6, 985ae06)
• ✅ login: crobert-1 / name: Curtis Robert (cc020d2)

[atoulme]

See CLA issues.

[rogercoll]

Seems to be related with the suggested applied commits. Could you take a look @crobert-1 ?

[crobert-1]

/easycla

[crobert-1]

My apologies, not sure what's going on here. I've filed a support ticket against EasyCLA, I'll share any relevant updates.

[crobert-1]

Ticket update:

On Friday we released co-author checks in EasyCLA. It seems there is a bug win the logic that is causing the missing ID on commit scenario. I am engaging our engineers to investigate this further. Thank you for reporting this issue.

[jarias-lfx]

/easycla