nix: add building oid to the flake

[JakeHillion]

OI's build is challenging and has often been a problem for the Open Source community. It requires an extremely specific set of dependencies that are very hard to achieve on most systems. There are frequent breakages, like when updating to CentOS Stream 9, or when trying to update the CI's clang from clang-12 to clang-15 - OI requires the clang libraries to be version 15 but can't be compiled with it on the CI!

This changes provides a mostly working build environment with nix. This environment is pinned to a specific nixpkgs revision using flake.lock, and only updates when we explicitly tell it to.

Summary of changes:

• Update CMakeLists.txt required version to 3.24. This allows specifying FIND_PACKAGE_ARGS in FetchContent, meaning we can use system packages. This is available on most up to date distros (3.30.2 is current).
• Extends flake.nix to be able to build OI. Adds instructions for building and developing OI using nix.
• Partially runs the tests in GitHub Actions. A huge amount must be excluded because of incompatibilites between the clangStdenv compiler and drgn. We have similar, though fewer, issues when building with the clang-12/libstdcxx mix on the Ubuntu 22.04 CircleCI, though this is at least reproducible.
• Updates CircleCI to build CMake from source as we don't have a newer image available. Also add some newly found dependencies (not sure how it was working without them before).

Test plan:

This change requires less testing than previous build related changes because it deprecates most of the build types.

• The internal BUCK build is unaffected. No special testing.
• The semi-internal CMake build is gone. Use Nix.
• The Nix build for clang-15 and some tests are continuously tested in GitHub actions.
• Tested the set of Nix commands in the README. All work except the one that points to GitHub as this must be merged first.
• The existing CircleCI runs on Ubuntu 20.04 are maintained.
• Unable to test the new test-report.yml as it must be merged due to the permissions it needs. Will follow up with testing after this is merged. See: https://github.com/dorny/test-reporter?tab=readme-ov-file#recommended-setup-for-public-repositories

The list of exclusions for GitHub Actions/nix testing is currently very long, I think 29% of the tests. This should be stable and reproducible though, and likely needs deep changes to OI to fix. That's why fixes are excluded from this PR. It's all to do with the forked drgn not being able to parse clang's newer DWARF output, and can't be fixed by rolling back as we required a relatively new libcxx.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 60.79%. Comparing base (79dca16) to head (375f3bd). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #502 +/- ## ======================================= Coverage 60.78% 60.79% ======================================= Files 126 126 Lines 12491 12491 Branches 2014 2014 ======================================= + Hits 7593 7594 +1 + Misses 3941 3940 -1 Partials 957 957 ```

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