Use maturin v1.0.0-beta.5 with PEP 704 (.venv) support

[konstin]

I recently add support to maturin to automatically use .venv from PEP 704 and i'm now trying to integrate this into real world projects.

Depending on your preference you might want to wait for the stable v1.0 maturin release before merging this.

[stinodego]

venv is a Make command that relies on the venv folder being present. We would have to rename that to .venv, which I think is fine but I'm not sure is allowed?

Update: Tested that, and it works.

[stinodego]

I'd be in favor of this change - I think .venv is more standardized as a folder than the current venv folder we use. But please do a search for venv through the code base, because there are some other spots where we rely on the venv folder, i.e. .gitignore and the Make command venv which should then be renamed to .venv.

Also, I think this change might also come in helpful in the CI?

And personally, I'd like to wait for the stable release, otherwise we'd have to update again when that comes out.

EDIT: Let me make that .venv rename change myself, then we can keep this PR purely for the maturin change.

[konstin]

rebase to avoid merge conflicts once #7790 is merged

[stinodego]

I'll close this for now, and open a new PR whenever maturin 1.0.0 comes out.