chore(version): v18.7.0

[janickm]

This pull request introduces a new release of the NCore project, version 18.7.0, with updates to the changelog and Bazel build configuration. The most important changes are the addition of new features, bug fixes, documentation improvements, and CI enhancements.

Release and build updates:

• Updated the project version to 18.7.0 in the ncore/BUILD.bazel file to reflect the new release.
• Added a detailed changelog entry for version 18.7.0 in CHANGELOG.md, documenting new features, bug fixes, documentation updates, and CI improvements.

Feature and bug fixes:

• Added timestamp_interval_us filtering to the get_cuboid_track_observations() function.
• Fixed an issue in the colmap module where downsampled images were included by default.

Documentation and CI improvements:

• Refined specifications for coordinate systems and transformations, and clarified lidar model documentation regarding azimuth offsets.
• Improved CI by preventing execution of non-build/test jobs in forks.