Fix clan template creation when already in a flake.
Currently we already fail with very clear and descriptive error when
trying to evaluate the template of the flake we are in:
```
Failed to select template 'flake-parts' from flake '/tmp/superclan' (via attribute path: /tmp/superclan#clanInternals.templates.clan."flake-parts")
```
This is undesired behavior.
When we are trying to create a clan with `clan flakes create`.
We can't rely on the fact that the flake we are currently in exports flake templates.
Now we *try* to evaluate the flake we are in upon creation.
If there are no clan templates available, we now will fall back to
builtin templates.
Closes: #4472
To execute the CLI in foreign directories
.#new-machine needs to get tranformed into /path/to/clan#new-machine
Otherwise it might pick-up some random flake that is in scope where the cli started executing
