cli: Support Converting PX4 ULog (.ulg) Files to MCAP

[amacneil]

Before Rust CLI 1.0, decide whether to support converting PX4 ULog (.ulg) files to MCAP.

ULog is a self-describing binary log format with embedded message definitions, so it should fit the same extension-based mcap convert dispatch model used for ROS 1 bag and ROS 2 db3 inputs.

[linear-code]

DB-613