Changes requested for libqasm Conan package

[rturrado]

Address this code review requested change for libqasm Conan package.

Fix CMake install:

• We were previously creating output folders in wrong places (e.g., include and src folders).

Move ANTLR's header files to include/v3x:

• generate_antlr_parser.py writes now output include files in a given include folder.

Remove unused type aliases from cqasm-types.hpp.

Update version.hpp, CHANGELOG.md, and test_cqasm.js to version 0.6.4.