feat(module/panorama): Add ability to define AMI ID for Panorama

[littlejo]

Description

I have a trouble of replacing EC2 panorama because ami can change. So i proposed to be able to set ami_id.

[sebastianczech]

/validate paths="modules/panorama"

Testing job ID: 6612175509 Job result: SUCCESS

[sebastianczech]

/plan paths="examples/panorama_standalone"

Testing job ID: 6612208319 Job result: SUCCESS

[littlejo]

Thank for putting in this PR all changes in code, which I asked in comments for #394, which was closed by you. Why previous PR was closed ?

I made a mistake in my Git commands.

[littlejo]

Hello, do you know what it's blocked ?

[sebastianczech]

If you create PR from fork, then our GitHub Actions doesn't allow automatically execute terraform plan (it's by design), that's why I was via ChatOps checking terraform validate and terraform plan:

• https://github.com/PaloAltoNetworks/terraform-aws-vmseries-modules/pull/395#issuecomment-1774923430
• https://github.com/PaloAltoNetworks/terraform-aws-vmseries-modules/pull/395#issuecomment-1774928967

Both pipeline finished successfully, so let's wait for one more review from other code owner and we will merge this PR