SPAR handles simplification (192)

It is proposed to get rid of ivas_spar_foa_enc_state_t handle and move its content directly to the SPAR_ENC_DATA. I.e. to define

typedef struct ivas_spar_enc_lib_t
{
ivas_spar_foa_md_enc_state_t *hMdEnc;
    IVAS_FB_MIXER_HANDLE hFbMixer;
    ivas_enc_cov_handler_state_t *hCovEnc;
    ivas_trans_det_state_t *hTranDet;
    ivas_agc_enc_state_t *hAgcEnc;
    int16_t dirac_to_spar_md_bands[DIRAC_MAX_NBANDS];
    int16_t enc_param_start_band;
    PCA_ENC_STATE *hPCA;
    int32_t core_nominal_brate;
 
} SPAR_ENC_DATA, *SPAR_ENC_HANDLE;

Similarly at the decoder.