feat: Enhance PagerDuty provider: fetch historical incidents & expand metadata

[onyedikachi-david]

/claim #1262

Closes #1262

📑 Description

This PR enhances the PagerDuty provider to fetch historical incidents and expand the metadata retrieved for each incident. Key changes include:

1. Modified the _get_alerts method to retrieve incidents from the past 30 days, with pagination support for up to 1000 incidents.
2. Added the include[] parameter to the PagerDuty API request to fetch additional incident details.
3. Expanded the _format_alert method to process and include comprehensive metadata such as acknowledgers, first trigger log entries, and conference bridge information.
4. Introduced DEFAULT_LOOKBACK_DAYS, MAX_INCIDENTS, and INCLUDE_DETAILS class attributes for easy configuration.

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

[vercel]

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[CLAassistant]

All committers have signed the CLA.

[Matvey-Kuk]

May I ask you to add a unittest for _format_alert make it easier for us to debug?

[onyedikachi-david]

@Matvey-Kuk GM, I don't know if you have found time to review the added test.

[Matvey-Kuk]

Closing due to #1262 (comment)