chore(general): use dependabot for python dependencies

[chpl]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Description

Add dependabot configuration for python (pip) packages

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my feature, policy, or fix is effective and works
• New and existing tests pass locally with my changes

[chpl]

this should automate things like

• fix(general): asteval to version 1.0.6 #7142
• fix(general): unpin boto3 and botocore versions #6071
• chore(general): upgrade Python module packaging #6952

[AdamDev]

Hi @chpl,
Could you please merge the latest changes from main into this branch?