implement timestep_init phases and catch up with master of ccpp-physics (2021/03/04)

[grantfirl]

Replaces #223

• Implement the timestep_init/finalize phases in SCM source code
• update to ccpp-physics master as of 2021/03/04
• change build system so that ccpp_prebuild.py writes caps/cmake snippets to build directory rather than src directory (this now works with the default CMakeLists.txt in ccpp-physics)
• change the diagnostic bucket clearing to SCM code
  -- change timing of diagnostic clearing (order of operations was wrong)
  -- allow for diagnostic clearing every timestep
• comment out reading in RUC LSM init variables since changes to ccpp-physics has rendered it obsolete (followup PR needed to read in RUC LSM init data)

[grantfirl]

Will likely need followup PR to accommodate recent changes in LSM initializations. The existing canned cases have been tested to work with this PR.

[grantfirl]

There are many whitespace changes in GFS_typedefs.F90/meta. This is on purpose to match changes in the FV3 versions of these files.

[grantfirl]

Associated with NCAR/ccpp-physics#562, which has already been merged.

[grantfirl]

@dustinswales This catches the SCM up with ccpp-physics master, including recently merged RRTMGP changes.