ci: various improvements in relation to --workspace support

[rvolosatovs]

Blocked by #2423

[haraldh]

Please also coverage.yml

[haraldh]

And adjust .codecov.yml line 3 with the number of matrix jobs in the coverage workflow

[rvolosatovs]

Looks like this PR is blocked on changes to https://github.com/profianinc/infra-terraform/blob/be9bd1afd473dfdb9087551ed883b5d2dac59ff1/github_branchprotections_enarx.tf#L60-L96 @puiterwijk ?

[codecov]

Codecov Report

Merging #2424 (575c184) into main (c95f593) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2424   +/-   ##
=======================================
  Coverage   58.63%   58.63%           
=======================================
  Files         201      201           
  Lines       12990    12990           
=======================================
  Hits         7617     7617           
  Misses       5373     5373           

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[bstrie]

Does every clippy check need to be its own action? Once one action has already done a full cargo clippy --workspace, the subsequent cargo clippy -p enarx-shim-kvm -p enarx-shim-sgx --target x86_64-unknown-none takes about 4 seconds, which doesn't seem worth the compute/transfer costs of spinning up a separate runner just do do those from scratch.