CMake: Make generate.py reusable

Make generate.py resuable outside of open-simh, as suggested and
motivated by Richard Cornwell's simulator repository.

- Make the "experimental" rule optional. Do not generate a Python
  "KeyError" if the rule is missing.

- Add documentation on how to use the CMake infrastructure outside
  of open-simh: Customize the packaging.py script, season to taste.

- Update the KA10 simulator customization, moving it to its own
  Python script, simgen/pdp10_simulator.py. Preparatory move that
  anticipates additional frontpanel and display options.

- generate.py option "--skip-orphans": Skip the orphaned simulator
  check (i.e., don't cross-reference the simulators in packaging.py
  with what was scraped from the makefile.)

- Add "TEST_ARGS" argument to CMake's add_simulator function so that the
  IBM 1130 simulator can pass to "-g" on the command line to disable the
  GUI when running RegisterSanityCheck, i.e.:

    ibm1130 RegisterSanityCheck -g

  This fixes an edge case Heisenbug encountered during Github CI/CD
  tests where ibm1130 appears to hang indefinitely on the Windows
  runners.

  The cause is the GUI's Pump() thread function being prematurely
  terminated before all GUI resources are acquired. The net result is an
  infinite loop in the MS C runtime trying to exit the process with
  unstable internal state. (Separate patch: synchronization across main
  and Pump() threads to ensure resource acquisition completes.)

  This issue never shows up on non-Windows platforms or the SIMH makefile.

- cmake/generator.py, cmake/simgen: Add a "test_args" keyword argument
  to the BasicSimulator constructor that holds the tests argument
  parameter emitted as the "TEST_ARGS" argument to a simulator's
  add_simulator(). Ensure that the IBM 1130 emits 'TEST_ARG "-g"' in its
  add_simulator().

- scp.c: reset_all_p() adds 'P' to the existing switches, versus saving
  sim_switches and ONLY setting the 'P' power-up reset switch. Net effect
  is that the IBM 1130 simulator actually sees the 'G' flag that inhibits
  the GUI during the console device reset.

README-CMake.md

@@ -1288,6 +1288,13 @@ add_simulator(simulator_name
     ## in its sim_instr() instruction simulation loop:
     USES_AIO
 
+    ## Arguments to append after "RegisterSanityCheck". These arguments
+    ## appear between "RegisterSanityCheck" and the test script, if
+    ## given, e.g.:
+    ##
+    ##    mysimulator RegisterSanityCheck -r -t path/to/mysim_test.ini
+    TEST_ARGS "-r"
+
     ## Packaging "family" (group) to which the simulator belongs,
     ## for packagers that support grouping (Windows: NSIS .exe,
     ## WIX .msi; macOS)
@@ -1386,9 +1393,19 @@ solution is `cmake/generate.py` to update the affected simulator
 ```sh
 ## You have to be in the cmake subdirectory to run the generate.py script
 $ cd cmake
+$ python -m generate --help
+usage: generate.py [-h] [--debug [DEBUG]] [--srcdir SRCDIR] [--orphans]
+
+SIMH simulator CMakeLists.txt generator.
+
+options:
+  -h, --help       show this help message and exit
+  --debug [DEBUG]  Debug level (0-3, 0 == off)
+  --srcdir SRCDIR  makefile source directory.
+  --orphans        Check for packaging orphans
+
 # [simh_source] is the absolute path to your top-level SIMH source directory
-$ python -m generate
-generate.py: Expecting to emit 77 simulators.
+$ python -m generate --orphans
 generate.py: Looking for makefile, starting in [simh-source]/open-simh/cmake
 generate.py: Looking for makefile, trying [simh-source]/open-simh
 generate.py: Processing [simh-source]/open-simh/makefile
@@ -1423,6 +1440,7 @@ generate.py: all target vaxstation4000m60
 generate.py: all target microvax3100m80
 generate.py: all target vaxstation4000vlc
 generate.py: all target infoserver1000
+generate.py: all target nd100
 generate.py: all target nova
 generate.py: all target eclipse
 generate.py: all target hp2100
@@ -1475,6 +1493,7 @@ generate.py: all target sel32
 generate.py: exp target alpha
 generate.py: exp target pdq3
 generate.py: exp target sage
+generate.py: Expecting to emit 78 simulators.
 ==== writing to [simh-source]/open-simh/3B2/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/ALTAIR/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/AltairZ80/CMakeLists.txt
@@ -1495,6 +1514,7 @@ generate.py: exp target sage
 ==== writing to [simh-source]/open-simh/Intel-Systems/scelbi/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/Interdata/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/LGP/CMakeLists.txt
+==== writing to [simh-source]/open-simh/ND100/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/NOVA/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/PDP1/CMakeLists.txt
 ==== writing to [simh-source]/open-simh/PDP10/CMakeLists.txt