Migrate Linode and DigitalOcean modules to Ansible collections (#14908)

Replace custom modules with official Ansible collection equivalents:
- linode_v4 → linode.cloud.instance
- linode_stackscript_v4 → linode.cloud.stackscript
- digital_ocean_floating_ip → community.digitalocean.digital_ocean_floating_ip

Changes:
- Add linode.cloud and community.digitalocean to requirements.yml
- Update roles/cloud-linode/tasks/main.yml (FQCN + api_token param)
- Update roles/cloud-digitalocean/tasks/main.yml (FQCN)
- Remove 3 entries from .ansible-lint mock_modules
- Delete 3 custom modules (519 lines removed)

Modules kept (no collection equivalent or deferred):
- x25519_pubkey.py - crypto-specific, no equivalent
- scaleway_compute.py - complex state machine, deferred
- lightsail_region_facts.py - no collection equivalent
- gcp_compute_location_info.py - no equivalent, google.cloud deprecated

Closes #14902

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: dguido

.ansible-lint

@@ -53,10 +53,7 @@ verbosity: 1
 mock_modules:
   - gcp_compute_location_info
   - lightsail_region_facts
-  - linode_stackscript_v4
   - x25519_pubkey
-  - linode_v4
   - scaleway_compute
-  - digital_ocean_floating_ip
 
 # vim: ft=yaml