Inconsisent search paths used for mission-provided files

[jphickey]

Is your feature request related to a problem? Please describe.
The CMake build system allows the user to provide customized versions of particular files by creating a file of the same name in the defs configuration directory. Specifically this feature is important for configuration header files and table files that are intended to be customized by the user.

The problem is that the search paths/patterns used for the cmake add_cfe_tables() function (for table files) and the generate_config_includefile() function (for headers) are not related at all, which is confusing.

Describe the solution you'd like
The search patterns and search order/priority levels between two functions should be more consistent, ideally use a common file finding function under the hood to implement the search, so the patterns and order will be the same.

Requester Info
Joseph Hickey, Vantage Systems, Inc.