Issue #67: Refactor window calculations for generality

[Mark2000]

Description

Closes #67

Refactors window calcs to be general while maintaining old ImagingSatellite API. Note: upcoming_opportunities is the one difference in the ImagingSatellite API.

Adds an upcoming downlink opportunity state. Can configure to include opening time or closing time.

Also addresses a small bug that happens in root finding where the root is found twice at nearly the same point.

How should this pull request be reviewed?

• By commit
• All changes at once

Type of change

• Bug fix (non-breaking change which fixes an issue)
• 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?

Added tests for new code. Maintains coverage.

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

Test Configuration

• Python: 3.10.11
• Basilisk: 2.2.1b0
• Platform: Mac 13.3

Checklist:

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

[LorenzzoQM]

Everything looks good!