Azure Batch validates the region before checking available VMs

[adamrtalbot]

If the Azure region was invalid (i.e. useast vs eastus) Nextflow would still check for regions. This PR checks for the existence of a region before checking for available VMs.

Additions:

• Nextflow checks for a valid region before checking the available VMs.
• This adds some very verbose logging which helps in debugging but might be too much.

TODO: ~- Confirm this will work with an unlisted region, allowing users to manually configure a pool in a region if the Nextflow set of regions is out of date.~ I've confirmed this works with an unlisted region by deleting the eastus entry demonstrating that Nextflow raises a warning into the console:

N E X T F L O W  ~  version 24.05.0-edge
Launching `https://github.com/nextflow-io/hello` [cheeky_hugle] DSL2 - revision: 7588c46ffe [master]
WARN: [AZURE BATCH] No location called eastus found! Please confirm it exists and the name is correct!
[fb/b8674b] Submitted process > sayHello (3)
[e1/275573] Submitted process > sayHello (1)
[5f/7bf8d5] Submitted process > sayHello (4)
[ad/1f8280] Submitted process > sayHello (2)