python3-pyproject-hooks: upgrade 1.0.0 -> 1.2.0

python3-pyproject-hooks: upgrade 1.0.0 -> 1.2.0

- Improve interoperability with importlib.metadata, fixing a regression
  in setuptools compatibility in 1.1 (#199).
- Clean up the _in_process directory inside the package from sys.path
  before imporing the backend (#193).
- Add type annotations to the public API.
- More careful handling of the backend-path key from pyproject.toml.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>