ci adjustments

* ubuntu:
  * only run jobs for "coverage" and "additional warnings" if the main ci build works
    and use its generated tarball in both cases
  * add two new artifacts: test binaries and windows source
* ubuntu+msys1+msys2+macos:
  * upload config.log after the build - because we may need it to debug build issues
  * always upload the testsuite.log (additional build documentation)
* ubuntu+msys1+msys2:
  * use --with-pkgversion to mark CI binaries
* msys1:
  * GMP url changes, building it again for performance reasons
  * building BDB with all relevant patches from MSYS2
  * drop GC install log step and therefore extra prefix
  * using msys-build instead of building Bison (only necessary for GC4)
  * drop extra CFLAGS previously necessary for local cJSON (fixed in 3.x)
  * enable NIST85 (+ comment-code in case we ever need to skip something there
    and/or ignoring failing NIST) --> as after last upstream update everything works
  * ci cache adjustment:
    * remove split per matrix
    * split per software, enabling smaller updates
  * use CI tarball like for the minimal build, drop flex+bison
  * drop workflow specific expected failures that now work fine
  * move env to MSYS job
  * resolve env vars by build API instead of runner
* integrate msys1.yml into ubuntu.yml, renaming to build_nightly.yml
* msys2:
  * split NIST + internal testsuite and run the later with less jobs to prevent hanging
* msys2+macos:
  * uploading NIST test results
* msvc: testsuite skip adjustments from the generated testsuite

temporarily disable (duplicate) PR builds