infra: add renovate

[emdneto]

Description

This Renovate config will:

• pin GitHub Actions by digest, use semantic commits, and apply the dependencies and Skip Changelog labels to Renovate PRs.
• Ignore Python dependency files like benchmark-requirements.txt|test-requirements.txt and pyproject.toml, while still scanning GitHub Actions workflow templates inside .github/workflows/templates/*.yml.j2 and .yaml.j2. + Locked files (i.e., test-requirements.{oldest,latest}.txt)
• Group updates in a cleaner way: documentation dependencies go into a docs deps group, GitHub Actions and Docker updates go into an infra group, patch updates for Python-related managers run on weekdays before 8am, and minor/major updates run on Monday before 8am (all UTC).

I believe renovate will fit better than Dependabot because we can configure as many packageRules as we want + ignore some paths. Also, this config solves a current problem with dependabot bumps: For Github Action workflows, most of the updates can't be applied because Dependabot updates workflows that are generated through tox -e generate-workflows, requiring a manual intervention step to update those. With this renovate config we are updating both templates+action workflows files.

See emdneto#5 to understand how many PRs will be open and which files are being tracked by this renovate setup.

[codeboten]

renovate has been really useful for years in the Collector repos, fully support moving to it