Remove linting and test files + setup from all starters

[merelcht]

Description

Remove all linting dependencies and configuration:

• setup.cfg completely
• linting config from pyproject.toml
• linting dependencies from requirements.txt: flake8, black, isort

Remove test setup:

• src/test directory completely
• pytest dependencies from requirements.txt

Update e2e test setup to still lint the starters by calling flake8, isort and black commands directly instead of kedro lint.

• To make these checks all pass we would need to add test setup for flake8, because the default max line length is 79 and we've always worked with a max lint length of 88.

Context

Follow up on: kedro-org/kedro#1849

[astrojuanlu]

Following the new utilities workflow kedro-org/kedro#2388 we'll keep these files.