Issue #86: Update BSK gravFactory

[Mark2000]

Description

Closes #86

Updates to use new bsk grav factory api

How should this pull request be reviewed?

• [ ] By commit
• [x] All changes at once

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• [x] Unit tests (General Environment only) pytest --cov bsk_rl/envs/general_satellite_tasking --cov-report term-missing tests/unittest
• [x] Integrated tests (General Environment only) pytest --cov bsk_rl/envs/general_satellite_tasking --cov-report term-missing tests/integration

Test Configuration

• Python: [e.g. 3.10.1]
  • Basilisk: [e.g. 2.2.0]
• Platform: [e.g. Ubuntu 22.08]

Checklist:

• [x] My code follows the style guidelines of this project (passes Black, ruff, and isort)
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] Commit messages are atomic, are in the form Issue #XXX: Message and have a useful message
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes