[C/C++] Install a CMake package configuration file

[ethanmusser]

Description

@swift-nav/algint-team

Install a CMake package configuration file.

This change permits downstream users configuring with CMake to include the SBP C bindings in their project as follows.

find_package(libsbp CONFIG REQUIRED)
target_link_libraries(my_target PRIVATE swiftnav::sbp)

Currently, those same consumers need to create a custom Findlibsbp.cmake find module script.

API compatibility

Does this change introduce a API compatibility risk?

No. This change simply adds to the installed files. The previous sbp-export target build tree export is preserved.

API compatibility plan

N/A

JIRA Reference

N/A

However, resolves #1528.