delay tigre import

[casperdcl]

• delay tigre imports so that documentation builds without TIGRE (fixes Move tigre imports to point of use, instead of at top of files using tigre #2322)
• fix cuda packages not required for some CI jobs

Probably related/required for:

• rattler-build #2321
• Update to support TIGRE v3 #2317
• numpy 2 #2218
• Remove code which has been deprecated since v24.3 or earlier #2309

Testing

Manually verified that the docs CI action:

• does not install tigre
• produces DocumentationHTML art[ie]fact which contains tigre plugin:

mkdir CIL; unzip -d CIL ~/Downloads/DocumentationHTML.zip
python -m http.server &
$BROWSER "http://localhost:8000/CIL/2323_merge/plugins/#tigre"

[lauramurgatroyd]

Hi @casperdcl I had been working on this locally and my version was almost identical to what you've done 👍