Upgrade async_timeout to 3.0.0

[fabaff]

Description:

• Drop Python 3.4, the minimal supported version is Python 3.5.3
• Provide type annotations

Example entry for configuration.yaml (if applicable):

http:

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

[fabaff]

Blocks #14517

[balloob]

Merge these 2 prs into 1 pr, as they are dependent on one another.

[fabaff]

Was the plan but something else interfered 😉