[lli] Revisit Orc debug output tests (#76822)

Integrate in-memory debug-info dumps into the `--orc-lazy-debug`
command-line option instead of exposing built-in functions to be called
from JITed code. This reduces overall amount of code (removing
`ExecutionUtils.cpp`) and seems cleaner anyway.

All existing items of `OrcDumpKind` work on IR level and run in the
IR-transform step of the JIT. The newly added `DumpDebugDescriptor` and
`DumpDebugObjects` must run after debug-registration and thus are
deferred to the Object-transform step of the JIT. This separation is the
major side-effect of the patch.