more nonsense build rearranging
more nonsense build rearranging

A few changes here:

- wrap internal static libs in declare_dependency, so that the include
  directories can be packaged up with the libraries. Less need to repeat
  'src' as an include directory
- merge tests into a single test-per-library. This still has the right
  output, and the tests are fast enough that we don't need to worry
  about overall runtime. Also, not enough tests that this will be a pain
  to sort through.
- drop the gtest_main library and include it as source. meson is smart
  enough to dedupe this for us.

falconindy/auracle,falconindy/auracle,falconindy/auracle