Due to different (old) glibc versions, DEATH was triggered in different
places on the cluster and on CI. This generalizes the DEATH message to
match on in the unit tests.
The public cvc5 API now lives in the cvc5 namespace. All internal parts were moved into the (new) internal namespace.
The final hierarchy will be as follows:
cvc5
~~ public API
::context
::internal
::parser
::main
After this PR it will be:
cvc5
~~ public API
::internal
::context
::main
::parser
Similar to #6031, this PR implements suggestions from iwyu to reduce the number of includes in header files by introducing forward declarations and moving includes to source files.