Remove METIS and GKlib from GitHub actions

[odow]

Follow-up to #2699

We need to remove the manually installed versions of metis and gklib in CI to ensure we're actually using the vendored copies.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.29%. Comparing base (cd2bd0b) to head (07bcb09).
⚠️ Report is 39 commits behind head on latest.

Additional details and impacted files

@@           Coverage Diff           @@
##           latest    #2702   +/-   ##
=======================================
  Coverage   81.29%   81.29%           
=======================================
  Files         349      349           
  Lines       85786    85786           
=======================================
+ Hits        69736    69738    +2     
+ Misses      16050    16048    -2     

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[odow]

There's a segfault in the unit tests which seems suspicious.

[filikat]

There's a segfault in the unit tests which seems suspicious.

That test is not compiled with HiPO, so it's a bit weird.
However, it made me realise two things that we are doing wrong @galabovaa:
1 - TestHipo.cpp should only be included in the unit tests if HIPO=ON.
2 - if solver=hipo is used in a build that does not include HiPO, at the moment IPX is selected, because of how lp_data/HighsSolve.cpp:useHipo is set up (line 724). It would be better to give the error in lp_data/HighsSolve.cpp:93, which I don't think is reachable at the moment.

[galabovaa]

Noted, @filikat

I've got updates to the workflows on a WIP branch. I have updated build_tarballs there too, so I'm closing this, @odow

[odow]

Can we please consider moving to a PR-based workflow over branches? It's hard to tell what people are working on.

[odow]

I think this is also a good motivation to simplify some of the CI workflows with a build matrix. We shouldn't need to copy-paste code in so many places. (e.g., where I was headed with #2551)

[galabovaa]

Thanks for the suggestion, but we will retain them for now