docs: [IAC-3191]: Update best practices re approvals

[richardblack-Harness]

Description

• Update IaCM best practice to include approval processes with links to dedicated docs for RBAC, Approval steps, and PR automation.
• JIRA

PRs must meet these requirements to be merged:

• Successful preview build.
• Code owner review.
• No merge conflicts.
• Release notes/new features docs: Feature/version released to at least one prod environment.

[bot-gitexp-user]

Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://67e2b25a850c6d20f15ade68--harness-developer.netlify.app

[richardblack-Harness]

@allofthesepeople Do you mind reviewing this

[bot-gitexp-user]

Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://67ee61e5208d8d03a6de68f9--harness-developer.netlify.app

[allofthesepeople]

nice expansion. Thanks!