[receiver/awscloudwatchreceiver] enable storage extension

[csatib02]

Description

This pull request enables the storage extension for the awscloudwatch receiver.
Previously, the receiver started collecting logs from time.Now().Add(-cfg.Logs.PollInterval). Unlike other receivers where the default behavior typically aims to retrieve all available logs by default, this receiver lacked flexibility. With the introduction of the storage extension, users now have more granular control over log collection.
To address this, I've added a new start_from field, allowing users to precisely specify their log retrieval preferences. This feature provides greater configuration options for users who want to limit log collection based on their specific requirements.

Link to tracking issue

Fixes: #32231

Testing

• Added unit tests to validate the persistence behavior
• Conducted thorough manual testing to ensure reliability

Documentation

• Updated README.md with new configuration options and usage details

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: csatib02 / name: Bence Csati (e388dd8, 078a861, 89a6f8a)

[atoulme]

Please address review comments and the build, and mark the PR ready to review again.

[dehaansa]

LGTM.

[atoulme]

@schmikei please review.

[schmikei]

I've been meaning to getting around and implementing this. Just tested it out and seems good to me. Thanks for adding the startFrom parameter and everyone else for giving initial glances.