feat: support static dependencies environment

[RaitoBezarius]

Description

Upstream distribution like NixOS prefer operating by constructing the dependency environment by themselves.

Here's a simple way to support that usecase by freezing the dependency environment.

Status

PROPOSED

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• nixos/opsdroid: init NixOS/nixpkgs#274848
• Run in production for a "This Week in NixOS" bot on Matrix.

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[jacobtomlinson]

I'm curious how this is different to setting no-dep on your modules?