github: Group+schedule GHA and Python updates and disable automerge

[bkeryan]

What does this Pull Request accomplish?

Reconfigure Renovate again:

• Set the timezone to US/Central for scheduling.
• Update GitHub Actions on weekends and group updates into a single PR.
• Update Python packages on weekends and group updates into a single PR.
• Move lock file maintenance to early Tuesday morning. This is primarily for indirect dependencies.
• Disable automerge because we don't need it with a less frequent update schedule.

Why should this Pull Request be merged?

Relying on lock file maintenance for all Python package updates has unexpected downsides:

• Python packages no longer show up in Dependency Dashboard
• The lock file maintenance PRs do not include changelogs for the updated dependencies

What testing has been done?

C:\Dev\nitypes-python2\.github>npx --yes --package renovate -- renovate-config-validator
 INFO: Validating renovate.json5
 INFO: Config validated successfully

[bkeryan]

Same as ni/nitypes-python#120

Note that Renovate can share configurations between repos and NI has a shared Renovate configuration in https://github.com/ni-kismet/renovate-configuration/tree/main but I'm currently configuring each repo separately.

[github-actions]

Test Results

   10 files  ±0     10 suites  ±0   19s ⏱️ ±0s
  150 tests ±0    150 ✅ ±0  0 💤 ±0  0 ❌ ±0 
1 470 runs  ±0  1 470 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 01fb1ae. ± Comparison against base commit d2a957b.