Handle configurations of hooks

As soon as hooks start to proliferate there will be more and more environment variables to configure them, I think we should consider that risk and think about alternatives, there could be a better approach. It is time for brainstorming:

• Do nothing, hooks will start to introduce env variables (there are already some of them), I think it could be a mess in the long term

• Use a json file to handle the configuration of all the hooks (shareable with a conan config install), the HookManager could pass those variables in every function call:

  hooks_config.json

  {
      "hook_name_1": {
          "key1": "value",
          "key2": "value"
      },
      "hook_name_2": {
          "...": "..."
      }
  }
  

  hooks/hook_name_1.py

  ...
  def pre_export(..., config):
      assert config == {"key1": "value", "key2": "value"}
      ...
  
  def post_package(..., config):
      ...
  

• add them to conan.conf file inside the cache

• ...more ideas?