LightGBM

[ci] remove Travis (fixes #3519) (#3672)

* [ci] move CI jobs from Travis to Azure DevOps (fixes #3519)

* comment out other CIs to avoid wasting cycles

* try without docker

* add container back

* stop using --user in pip install

* run check-docs and lint without container

* job names

* move more jobs to Azure-hosted Linux pool

* fix PATH for check-docs

* uncomment other CI

* uncomment windows

* remove uses of maxParallel

* try moving macos-latest jobs to GitHub Actions

* fix config

* fix missing conda env

* set Python version

* remove commented-out code

* add more to GitHub Actions

* try to fix GPU

* remove static_analysis to prevent conflicts with #3726

* change workflow name

* try using ubuntu:latest docker

* fix conda

* trying to find where permissions first break

* add workaround for sudo

* please azure please

* image syntax

* more sudo

* noninteractive

* LC_ALL

* more  sudo

* more stuff

* CONDA dir

* paths

* get path

* missing CONDA

* fix path stuff

* more tests

* fix graphviz

* stuff

* more graphviz

* install xorg-libxau

* graphviz works, run more jobs

* stuff

* enable more tests

* uncomment GitHub Actions

* uncomment all other CIs

* Apply suggestions from code review

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* add travis.yml to Rbuildignore

* add Rbuildignore rule for fmt

* add libomp for clang builds

* changes from code review

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>