Make a custom Cargo profile for colcon

[m-dahl]

We want to do:

[profile.colcon]
inherits = "release"

This would allow us to cut down on build times when compilation is invoked both from colcon and cargo at different times. However this is not yet in stable cargo, so we should revisit this when rust-lang/cargo#6988 is merged.

Until then we use the release profile for colcon builds which allows using the debug profile for cargo builds.