[CMake] Decouple prim_ops from executorch

[kirklandsign]

🚀 The feature, motivation and pitch

Right now we have executorch_core, and executorch(= executorch_core + prim_ops).

This is confusing, when people depend on executorch. Make prim_ops a separate library instead.

Similarly, we might need to revisit BUCK runtime/executor:program vs runtime/executor:program_no_prim_ops

Alternatives

No response

Additional context

No response

RFC (Optional)

No response

cc @larryliu0820 @jathu

[kirklandsign]

• Vulkan tests use executorch_core #10765
• Test.cmake use executorch_core #10747
• Kernels should depend on executorch_core #10738
• extension/module doesn't depend on prim_ops #10710
• [CMake] data_loader and runner_util use executorch_core #10703
• [CMake] llm_runner use executorch_core #10698
• extension/module should depend on executorch_core #10678
• kernel/portable deps on executorch_core only #10674
• No need to expose executorch dependency executorch_core #10673
• Tests use executorch_core #10764
• [TEST] Split prim ops into its own #10741