Add support for the new composer installed.json format

[sixcare]

Composer has release version 2.0 and with it follows a new format for installed.json.

vendor/composer/installed.json format changed:

packages are now wrapped into a "packages" top level key instead of the whole file being the package array
packages now contain an "installed-path" key which lists where they were installed
there is a top level "dev" key which stores whether dev requirements were installed or not

This new format breaks project kernel:

PHP Warning:  Uncaught TypeError: Argument 4 passed to Aura\Project_Kernel\Project::__construct() must be of the type array, object given, called in /var/www/test/vendor/aura/project-kernel/src/Factory.php on line 122 and defined in /var/www/test/vendor/aura/project-kernel/src/Project.php:79
Stack trace:
#0 /var/www/test/vendor/aura/project-kernel/src/Factory.php(122): Aura\Project_Kernel\Project->__construct()
#1 /var/www/test/vendor/aura/project-kernel/src/Factory.php(82): Aura\Project_Kernel\Factory->newProject()
#2 /var/www/test/vendor/aura/project-kernel/src/Factory.php(48): Aura\Project_Kernel\Factory->newContainer()
#3 /var/www/test/web/index.php(15): Aura\Project_Kernel\Factory->newKernel()
#4 php shell code(1): include('/var/www/test...')
#5 {main}
  thrown in /var/www/test/vendor/aura/project-kernel/src/Project.php on line 79

https://github.com/auraphp/Aura.Project_Kernel/blob/2.x/src/Project.php#L79

Composer version 2.0.8 2020-12-03 17:20:38

Steps To Reproduce

Update composer via: composer selfupdate --snapshot
Run composer update