Suggest users install with pip install of using hatch

[jemrobinson]

:white_check_mark: Checklist

• [x] I have searched open and closed issues for duplicates
• [x] This is a request for a change to documentation
• [x] This isn't a feature request or bug report
• [x] This isn't an open-ended question (open a discussion if it is).

:ledger: Where is the problem?

Using hatch is overly complicated for end users. We should suggest they install with pip instead.

:memo: Required documentation changes

Update hatch references

[JimMadge]

A few things we need to be careful about,

• (How) do we enforce a strict set of pinned dependencies like in the requirements.txt. That is currently don't with a hatch pre-install hook
• I think we have files that wouldn't be included in a wheel build (non-python files in data_safe_haven)