[ServoController] Fix serial packet handling and error propagation

[soonhyo]

On HIRO running QNX, partial serial reads could leave bytes from a previous transaction and cause subsequent requests to fail across servo IDs. Synchronous packet dumps also delayed service calls.

This PR:

• Handles partial I/O with timeouts, validates frames, and serializes transactions.
• Propagates communication failures and validates angle arrays and joint groups.
• Makes packet dumps optional with SERVO_SERIAL_DEBUG (default OFF), while
  retaining error messages.
• Adds optional Linux PTY regression tests through CMake/CTest.

Service signatures are unchanged. C++ consumers of ServoSerial.h must rebuild.

Regression tests passed with logging enabled and disabled.
Corresponding changes were tested on HIRO running QNX.

The protocol still cannot distinguish a late reply to an identical request.

[k-okada]

@soonhyo nice!, btw did HIRO ues fkanehiro/master branch?

[soonhyo]

@soonhyo nice!, btw did HIRO ues fkanehiro/master branch?

HIRO uses pazeshun/hrpsys-base’s hironxjsk-devel branch. I’ve closed this PR and opened two new PRs: one targeting fkanehiro/master (#1342 ) and another targeting hironxjsk-devel (pazeshun#1).