Add TOA albedo/reflectance in CRTM

[chengdang]

Add TOA albedo/reflectance in CRTM forward/TL/AD calculations

• [x] Merge initial implementation from v2.4.1 into v3.
• [ ] Add TL/AD calculations.
• [ ] Add forward/TL/AD unit tests.
• [x] Add TOA reflectance in all RTS I/O interfaces.
• [ ] Offline scientific tests for computed forward/TL/AD calculations.

[chengdang]

With the CRTM V3 updates, solar_irradiance has been added in RTS data structure (not by me). Both TOA downward solar irradiance and computed radiance are saved as part of the standard outputs, where:

RTV%Solar_Irradiance       = SC(SensorIndex)%Solar_Irradiance(ChannelIndex) * GeometryInfo%AU_ratio2
RTSolution%Solar_Irradiance = RTV%Solar_Irradiance

RTV%Down_Solar_Radiance = cosine_u0*EXP(-RTV%Total_OD/cosine_u0)*Solar_Irradiance/PI 
RTSolution%Down_Solar_Radiance     = RTV%Down_Solar_Radiance

NOTE: (1) Solar_Irradiance is solar irradiance at TOA. (2) Down_Solar_Radiance is solar radiance that reaches the surface, which only gets output/computed with emission model.

[chengdang]

Initial implementations on TOA reflectance are added in branch: https://github.com/JCSDA/CRTMv3/tree/feature/cd_TOA_R

Introduced the TOA reflectance in RTSolution as Reflectance: https://github.com/JCSDA/CRTMv3/blob/621601bd5f915daec29a2da338460838ae3a33f4/src/RTSolution/CRTM_RTSolution_Define.f90#L234

Which is computed with the following formula in Common_RTSolution.f90

    ! -------------------------------------------------------
    ! Compute the corresponding solar reflectance (TOA only)
    ! -------------------------------------------------------
    IF( RTV%Solar_Flag_true .AND. (.NOT.(RTV%aircraft%rt))) THEN
      RTSolution%Reflectance = RTSolution%Radiance/(RTV%COS_SUN*RTV%Solar_irradiance/PI)
    END IF

With the following notes:

• Reflectance is only computed when solar flag is true (solar channel, solar irradiance > 0, and solar zenith angle < 85).
• Reflectance is only computed for TOA (i.e., RTV%aircraft%rt = .FALSE.) because CRTM does not computed added downwelling radiance at model layers.
• Downwelling TOA cosmic background radiance is zero/neglected at solar channels.
• Reflectance defined in this way can be much larger than 1, because RTSolution%Radiance also includes emitted radiance, an example would be the reflectances computed for abi_g18.

[chengdang]

TL/K_matrix reflectance implementation are pending per issue #89.