Re-implement state import without tfid

[kklimonda-cl]

Description

We want to drop Tfid attribute that is now common between all resources, and instead make use of the fact that the terraform ID used during state import can be any string value.

The new interface for creating import id would be based on provider functions, introduced in Terraform 1.8 and OpenTofu 1.8:

data "panos_address_group" "test_group" {
  location = {
    shared               = true
    from_panorama_shared = false
  }

  name = "test-group"
}

output "test_group_import_id" {
  value = provider::panos::create_import_id("panos_address_group", data.panos_address_group.test_group)
}

Implementation

• Make Terraform Locations marshallable from/to JSON
• Create new structures that describe Import ID (location, names etc.) and can be marshalled to/from JSON
• Implement create_import_id Terraform function to convert resources into import IDs #150
• Create per-resource functions to generate import id base64 data #149
• Update ImportState code to properly unmarshal JSON and prepare new resource for the Read() call
• Remove Tfid from across the codebase