Default build type: Release or Debug?

Problem

If I'm not mistaken, the default build type is now Debug and used to be Release. I don't know if/when this actually changed. But we should probably make this easier for the user to see and/or change. For a user who does not know this, they could be accidentally using a debug build, which (from a rigorous study with N=1) could be close to 100x slower.

Solution

• Include details in the documentation on how to switch between Release and Debug builds (and why)
• Print a message in CMakeLists clarifying what the current build is

Additional context

I tested this on an M4 Mac, building from source. I would like to hear from others if the default build type is different for different ways of building. @mrp089 @ktbolt since you built on different systems (for the SimTK binaries maybe?), do you know if it is always debug?

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

Start by inspecting the CMakeLists file and the existing build documentation to determine how the default build type is selected. Verify the behavior across the build paths mentioned in the issue before making changes. Done means the documentation explains how and why to switch between Release and Debug, and the CMake configuration clearly reports the current build type.