hwmv2: boards: intel_adsp: Overhaul board configurations

Rename and join configurations for intel_adsp CAVS and ACE
boards to benefit from HWMv2 shortened names with resulting
names change:

  `intel_adsp_ace15_mtpm` --> `intel_adsp/ace15_mtpm`
  `intel_adsp_ace20_lnl`  --> `intel_adsp/ace20_lnl`

Signed-off-by: Dmitrii Golovanov <dmitrii.golovanov@intel.com>