CI: move `build-contracts-doc` jobs to a separate stage, bump dependencies

Description

Problem: build-contracts-doc job is in the same stage as build-all job that builds all haskell components, so these jobs run in parallel. But nix derivation for build-contracts-doc depends on the haskell packages as well. Because of that building of haskell packages happens in both jobs, which makes haskell compilation errors harder to find, and also puts excessive load on CI

Solution: move both build-contracts-doc jobs to a separate stage. Now haskell compilation errors will always be in the build-all job

Related issue(s)

None

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Related changes (conditional)

• Tests (see short guidelines)

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • Root README and other README.md files
    • Haddock
    • docs/
  • I updated changelog files of all affected packages released to Hackage if my changes are externally visible.

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