[Realtime] Remove cudaq-realtime components that depend on CUDA-Q

[1tnguyen]

Description

As cudaq-realtime is expected to be a standalone library, remove components that explicitly depend on CUDA-Q:

(1) cudaq_compiler: a CUDA-Q based implementation of the compiler interface.

Note: this PR doesn't remove the abstract compiler interface and those associated classes (e.g., qcontrol_program)

(2) Helper functions supporting string manipulation of CUDA-Q MLIR strings.

(3) The MLIR pass to support lowering cudaq::device_call into __nvqlink_device_call_dispatch function call.

Note: this plugin is currently detached (commented out) from the CMake build config.
If needed, we could port this pass to the main CUDA-Q repo.

Also, rename a namespace reference to cudaqx and the default install directory.