Prepare 1.6.0 release (#2642)

* Add list of merged prs

* Remove branch trigger

* Update release instructions

* Include 9.2.1 in the current release

* Bump up hls version

* remove duplicate mention

* Remove references to branch name

* Fix cabal.project gen

* Correct fail-fast condition

* Bump up minor version

* Bump up major version

* Bump up major version

* Allow brittany only for 9.0.1

* brittany not supported in hackage and 9.0.2

* Not short hls for hackage

* Bump up versions everywhere

* Update hackage index

* Add ghcide in rename plugin

* Apply linter and add selection demo

* Add header linkable

* Add first version of release description

* Add last prs

* Mention wingman

* Grammar corrections

Co-authored-by: Jan Hrcek <2716069+jhrcek@users.noreply.github.com>

* Correct mention

Co-authored-by: Pepe Iborra <pepeiborra@me.com>

* Warn about th in docs

* Remove reference to install doc

* Rephrasing

Co-authored-by: J. S. <document_done@hotmail.com>

* Better style

Co-authored-by: Junyoung "Clare" Jang <jjc9310@gmail.com>

* Use could to stress it likely will not work

* REmove reliable from the warning

* Reorder comments

* Rephrasing

Co-authored-by: Michael Peyton Jones <me@michaelpj.com>

* Update docs/supported-versions.md

Co-authored-by: Michael Peyton Jones <me@michaelpj.com>

* Use last version of internal deps

* Restore original wording

* One more pr

* One more pr

Co-authored-by: Jan Hrcek <2716069+jhrcek@users.noreply.github.com>
Co-authored-by: Pepe Iborra <pepeiborra@me.com>
Co-authored-by: J. S. <document_done@hotmail.com>
Co-authored-by: Junyoung "Clare" Jang <jjc9310@gmail.com>
Co-authored-by: Michael Peyton Jones <me@michaelpj.com>