Merge pull request heroku#465 from heroku/develop

v190

Merge pull request heroku#461 from heroku/develop

v189

Merge pull request heroku#458 from heroku/develop

v188

Merge pull request heroku#453 from heroku/develop

v187

Merge pull request heroku#449 from heroku/develop

PHP 8.0.0 and the other usual updates

Merge pull request heroku#448 from heroku/develop

Fix composer bin-dir $PATH settings

Merge pull request heroku#447 from heroku/develop

Composer 2 support

Merge pull request heroku#445 from heroku/develop

v183

Merge pull request heroku#439 from heroku/heroku-20

Support heroku-20

Merge pull request heroku#436 from heroku/develop

v181