set package index asserts expensive

Hack around wrong .mix directories for tests

and with `optimization: False`.

Force cabal to use a build plan where exe:cabal-plan is enabled

Remove redundant init message for hackage dir name

Provide more context in error messages

[ci skip]

Add unit tests for the `MessageUtils` module in the cabal-install-solver package.

Fail reason now includes suggestions for misspelled language extensions
and language standard.

Add changelog entry for #7250

Fix #7460

standalone tests for `cabal init`

Print error message if no freeze file can be found