Compute bearings from OMF transportation and refactor of serialization process

[yamilbknsu]

This PR implements the functionality of computing edge bearings using the last line in the LineString geometry and refactors the serialization into csv/txt code to be a little cleaner.

This would be last remaining attribute in #57 , however, I noticed the speed by class mapping now returns speed for only 3 classes, which may be an indication that at some point we are filtering too much? I'll take a look to see if I find some bug.

closes #57

[Copilot]

Pull request overview

This PR implements edge bearing computation from LineString geometries and refactors the serialization process for compass datasets. The bearing computation addresses the "headings" requirement mentioned in issue #57.

Changes:

• Added bearing_deg_from_geometries function to compute bearings from the last two points in LineString geometries
• Refactored serialization code by extracting common patterns into reusable serialize_into_csv and serialize_into_enumerated_txt functions in the util/fs module
• Added bearings field to OmfEdgeList struct and corresponding serialization output

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
rust/bambam-omf/src/util/fs.rs	Added generic serialization functions for CSV and enumerated text files with progress bars
rust/bambam-omf/src/graph/serialize_ops.rs	Added bearing computation function using geo library's Haversine bearing calculation
rust/bambam-omf/src/graph/omf_graph.rs	Integrated bearing computation into graph generation, refactored serialization to use new utility functions, and added filename constants

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[robfitzgerald]

let's just roll this one in. thank you!