[Test] Networking setup: honor the AZ allowlisting everywhere in the networking setup and exclude eu-west-2d.

[gmarciani]

Description of changes

Honor the AZ allowlisting everywhere in the networking setup and exclude eu-west-2d.

Before this change, only the default AZ was honoring the allowlisting, so other components such as the ODCR stack had chances to select unexpected AZs.

With this change, by default all the region's AZs are usable, but if the region has an explicit allowlisting, only those allowlisted AZs will be considered.

As part of this change we set the allowlisting for eu-west-2, where we exclude eu-west-2d which is a new AZ that does not support our default instance type c5.xlarge.

Tests

SUCCESS

test-suites:
  update:
    test_update.py::test_multi_az_create_and_update:
      dimensions:
        - regions: ["eu-west-2"]
          schedulers: ["slurm"]
          oss: [{{ OS_X86_1 }}]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
  storage:
    test_fsx_lustre.py::test_multi_az_fsx:
      dimensions:
        - regions: ["eu-west-2"]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
          oss: [{{ LUSTRE_OS_X86_1 }}]
          schedulers: ["slurm"]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.