Update kedro pipeline create to match starters template for tests

[ankatiyar]

Description

The pipeline tests in the starters are in <project_root>/tests/pipelines> and when you create a new pipeline using the kedro pipeline create, the test files are created in src/tests/pipelines`.

Context

For eg - the project was created with spaceflights-pandas starter and pipeline2 and pipeline3 were created with kedro pipeline create and this is the resulting project structure -

Expected Result

Quoting @astrojuanlu -

in my opinion we should put them under <project_root>/tests, and avoid shipping them. that was the spirit of the template rework at least, probably we forgot to update kedro pipeline create accordingly

[astrojuanlu]

tests was moved out of src in #2926

[julnow]

I think it should be updated accordingly in docs, for example here: https://docs.kedro.org/en/stable/development/automated_testing.html#set-up-automated-testing-with-pytest
It still shows the old structure, so with tests under src directory.