Use Pretty/Parsec in Init (remote Text Category instance)

Resolve #6589: Remove -any and -none syntax

Change BuildReports parse/pretty to use FieldGrammar framework

More described

The +/- prefix is now mandatory.

Remove text instances

Remove -any and -none from Described VersionRange

Add weeder

Add Described PackageIdentifier and RelaxDeps

Remove Text RelaxDeps instances

Resolve #5570: Use PackageVersionConstraint more

Update documentation to reflect that `cabal init` is not interactive by default in 3.0

Since `cabal init` is no longer interactive by default
(as per my version, 3.0.0.0), including other minor
changes to the `init` process, change the `cabal init`
section to mention the usage of the `--interactive` flag,
and the new minor changes (which/the order questions
are asked, what the terminal output is).

I came across this problem while learning `cabal`
(having recently migrated from `stack`) and reading
this section of Cabal's quickstart guide.

To be proactive, add TIP relatively-linking to the
new getting started guide
(https://cabal.readthedocs.io/en/latest/getting-started.html)
in a TIP at the top of the page.  Implemented
because that is the best "entrypoint" to the docs,
but many resources/searches still point the user
to this page being modified.

Internal refactorings to install command.

Add Described PackageVersionConstraint

First step towards https://github.com/haskell/cabal/issues/5570

This simply extract logic out of installAction into separate helper
functions. This makes the inputs to each of these explicit and removes data
dependencies from a distance. This will make it easier in the future to pull out
behaviour to be shared between the 'install' command and the 'env' command.

Cabal.Distribution.Compiler: add Functor, Foldable, and Traversable instances for PerCompilerFlavor

Add active-repositories configuration