Add support for importing remote files?

[nuwang]

TPV already supports including multiple remote config files through job_conf.yml. However, it may also be worthwhile enabling TPV config files to be composed of multiple smaller files through an import section.

e.g.:
mylocal_tpv_conf.yml

global:
   import:
      - https://github.com/galaxyproject/tpv-shared-database/blob/main/tools.yml
      - https://raw.githubusercontent.com/usegalaxy-au/infrastructure/master/files/galaxy/dynamic_job_rules/production/total_perspective_vortex/tools.yml
      - https://raw.githubusercontent.com/usegalaxy-au/infrastructure/master/files/galaxy/dynamic_job_rules/production/total_perspective_vortex/users.yml
      - https://raw.githubusercontent.com/usegalaxy-au/infrastructure/master/files/galaxy/dynamic_job_rules/production/total_perspective_vortex/destinations.yml

tools:
  # my tool overrides
  ....

users:
  # my user overrides
  ....
 

Advantages:

1. Allow more complex tpv configurations to be refactored into multiple smaller files, without breaking users
2. Aggregate multiple files into a single file that others can just import

This is more with a view to future proofing than actual current necessity, but maybe there are more use cases?