Current proj.db build time is typically 50 to 60 seconds (and up to 7.5
hours on arm64 cross-compilation with full emulation!). Most of it is
due to running consistency checks. Those checks actually only need to run
once each time when we update the content of the database. When skipping
them, the build time is cut to 3 seconds or so.
So in data/CMakeLists.txt, let keep track of an expected md5sum
resulting from the concatenation of the data/sql/*.sql files. When
building proj.db, we check if the got and expected md5sum match. If they
do build proj.db by inserting the consistency check triggers after
having inserted data record. If there's a mismatch, do a one time build
with the triggers inserted before the data records, check that proj.db
builds fine with that, and if so, emit a CMake error message indicating
to the user that they must update the PROJ_DB_SQL_EXPECTED_MD5 variable
in data/CMakeLists.txt with the provided value. Next runs will go
through the fast build path, until content is updated again.

…d WKT ESRI

Fixes OSGeo#4281