Update csv and dialyxir, improve CI

Update versions of build-time, development and test dependencies.

The csv package bumps major versions but the changes do not affect us.

As for dialyxir, the later minor version fixes a potential problem with more recent versions of Elixir (1.15 and up).

While we’re at it, improve the CI pipeline so that expensive operations, such as downloading dependencies or compiling, are cached.