Backport - get_octopusvariable safely for python

[mik-ky]

Backport of #1043, which is already present in 2023.3+ onwards.

Also cherry-picks two commits to fix test failures:

• #1107
• #1047 - This change is present in the latest tag for 2023.2 (25.5.9-hotfix3) but has not made its way into this LTS branch.

Relates to https://github.com/OctopusDeploy/Issues/issues/8175