Changes to build with qt6

[Yadunund]

Adopted pattern similar to rviz_default_plugins to address #229

[mintar]

The check is failing, could you have a look?

[Yadunund]

@mintar the failing package is imu_complementary_filter which is not affected by changes in this PR. But I can take a look~

[Yadunund]

I was able to build imu_complementary_filter from source within a ROS 2 Rolling workspace (core also built from source). Wondering if the Docker image that is pulled by the Github Action is outdated.

[mintar]

Ah right, that's probably the case. This build failure was caused by an upstream change, and the Docker image will only be updated after the next release. I'll merge this, thanks!