Install requirements for integrations in packages before importing them.

[ludeeus]

Description:

This change will install the requirements of integrations (if any) before trying to import it.

If the integration import has imports from external packages in the top (not in a function/method) you will get this error on config_check and startup if the configuration for that integration is in a package instead of directly in configuration,yaml:

Package package_name setup failed. Component integration_name does not exist

Related issue (if applicable): fixes #24954 fixes #24720

There is also an issue with Yellight could not find a related issue for it but it was reported in #devs_general

After the move to manifest.json for requirements, more and more integrations will start to get this issue as well.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
  Travis and CircleCI passed in my fork.
• There is no commented out code in this PR.
• I have followed the development checklist

[Kane610]

I think this might solve the unifi device tracker issue as well. It works if a config entry exists but else it will fail with a similar message