Make sure all symbols exported by our shared library are prefixed with ldb_ in CI/CD

[Ngalstyan4]

Bad things happen if two postgres extensions define symbols having the same name.

Make sure CI/CD fails if this is detected.
Related to #145 and can probably use the same pipeline

sidenote: you can compare what are the common symbols exported by a pair of object files like this::
comm -12 <(nm -gD ./lantern.so | awk '{print $3}'| sort ) <(nm -gD ~/pgvector/vector.so | awk '{print $3}'| sort)