linux: updateScript: use upstream declarations and website generation scripts rather than parsing the website

[Atemu]

Issue description

Currently, the kernel updates script parses the kernel.org website to figure out which releases are supported and which is the newest version for each.

I had a look at how that website is generated and it appears it's this script which uses this python config file as its ground truth.

The upstream script looks well engineered at a glance and likely could be used for our purposes without requiring any upstream changes but I didn't look too closely.

The current script seems to be working just fine, so there isn't any urgent need to change it but IMHO this would make for a much better API than parsing the HTML which this script generates and it's python on both ends too.

cc @K900 @alyssais @TredwellGit @Ma27 @NeQuissimus