Bumping debcompat version in bloom

[nuclearsandwich]

Updating the debhelper compatibility version in bloom will trigger changes for all downstream packages in ROS 2.

To mitigate the risks of rolling this out and steadily fielding breakages. Before it receives wide release, I'd like to run a test build of Rolling using packages bloomed with a pre-release that includes the compat version change.

Continue iterating on this in #643

• custom rosdistro branch with rosdistro migration tools used to create modified bloom templates for each package.
• custom release build configuration for this distro that disables parallelism, on by default in debhelper>=10
• colcon-ros-buildfarm results from this build compared to rolling at the time of snapshot.

After initial tests are completed, we'll announce and release this change as part of bloom 1.0.0.