Reuse bond heartbeat watchdog timer

[mini-1235]

This came up while I was doing some lifecycle manager performance work in Nav2. In summary, this PR includes the following changes:

Bond::heartbeatTimerReset() now reuses the existing heartbeat watchdog timer instead of destroying and recreating it on every heartbeat. The first heartbeat still creates the timer, while subsequent heartbeats call TimerBase::reset() to renew the deadline. This preserves the intended watchdog behavior without changing the heartbeat frequency or timeout duration. In my 2-minute performance test, this gives a small improvement of about 2%, but since this is related to heartbeat_timeout_, I think it is still worth optimizing.

This PR also narrows the included rclcpp headers to help reduce build time, and updates the minimum CMake version.

Assisted by Codex 5.6 Sol

[mini-1235]

cc @SteveMacenski

Could you also take a look at this one? It is related to ros-navigation/navigation2#6061, and you are more familiar with this part of the code than I am.

[SteveMacenski]

This seems to work I think. heartbeat_timeout_ can change using setHeartbeatTimeout but since it doesn't change when started_, its OK as this only occurs after its started.

[SteveMacenski]

Just adding the comment for a future reviewer that I'm sure will want to track down the same thing.