Install corepack@0.31.0 instead of hardcoding integrity keys

[ravicious]

Closes #51796.
Ent PR: https://github.com/gravitational/teleport.e/pull/6008

In #51761, I initially just hardcoded the keys used by corepack to avoid updating the tooling. The whole situation seemed a bit fishy to me and the solution of "Just update corepack to the newest version" seemed to me on par with "Just ignore integrity checks", in that in the heat of the moment it'd be the simplest change to make which would unblock the rest of the team but also potentially introduce a malicious code to the project.

The dust has settled a bit since yesterday and following Fred's advice, I'm replacing the hardcoded keys with an updated version of corepack which has those updated keys baked in. Initially I thought we'd be able to remove the env var with keys when we'll get around to updating our Node.js version. But this might take some time and there's no guarantees that the new Node.js version used by Electron is going to actually have corepack >= 0.31.0.

We should still get rid of npm install -g corepack@0.31.0 once we update Node.js to a version that comes with corepack >= 0.31.0, this has been reflected in build.assets/versions.mk.

I made a successful tag build with this PR and the ent PR. https://github.com/gravitational/teleport.e/actions/runs/13133912317

[codingllama]

This is certainly nicer, thanks @ravicious!