hdc-algo utils & linspace

[valpesendorfer]

This PR adds a utils module for simple utility function that shouldn't necessarily go into ops.

Now I've added to_linspace which has functionality copied over from hdc-tools, to map an input array into linear space. This is useful for using the grouped aggregations introduced in 0.3.0

I've also extended the PeriodAccessors which a linspace property, as this is likely one major usecase. In this specific case, the linear array is just the yearly index with 0-index. Still, IMO it's useful to abstract this away so that can be used as direct input.

Edit:

PR also includes:

• bump and application of new black version
• bump of github actions
• bump of S3 credential action from v2 to v4 - default cred timeout is now 1h (should be plenty), and need to verbosely set AWS account ID to masked