shared_bindings_matrix: Run in parallel

.. this makes it take a fraction of the time, at least on systems
with a lot of CPU threads.  Even on my old laptop with a 2-core CPU
it reduces the time from 55s to 27s.

docs/shared_bindings_matrix.py

@@ -28,6 +28,7 @@ import re
 import subprocess
 import sys
 
+from concurrent.futures import ThreadPoolExecutor
 
 SUPPORTED_PORTS = ['atmel-samd', 'esp32s2', 'litex', 'mimxrt10xx', 'nrf', 'stm']
 
@@ -131,22 +132,24 @@ def lookup_setting(settings, key, default=''):
         key = value[2:-1]
     return value
 
+def all_ports_all_boards(ports=SUPPORTED_PORTS):
+    for port in ports:
+
+        port_dir = get_circuitpython_root_dir() / "ports" / port
+        for entry in (port_dir / "boards").iterdir():
+            if not entry.is_dir():
+                continue
+            yield (port, entry)
+
 def support_matrix_by_board(use_branded_name=True):
     """ Compiles a list of the available core modules available for each
         board.
     """
     base = build_module_map()
 
-    boards = dict()
-    for port in SUPPORTED_PORTS:
-
+    def support_matrix(arg):
+        port, entry = arg
         port_dir = get_circuitpython_root_dir() / "ports" / port
-        for entry in (port_dir / "boards").iterdir():
-            if not entry.is_dir():
-                continue
-            board_modules = []
-            board_name = entry.name
-
         settings = get_settings_from_makefile(str(port_dir), entry.name)
 
         if use_branded_name:
@@ -162,7 +165,11 @@ def support_matrix_by_board(use_branded_name=True):
             key = f'CIRCUITPY_{module.upper()}'
             if int(lookup_setting(settings, key, '0')):
                 board_modules.append(base[module]['name'])
-            boards[board_name] = sorted(board_modules)
+
+        return (board_name, sorted(board_modules))
+
+    executor = ThreadPoolExecutor(max_workers=os.cpu_count())
+    boards = dict(sorted(executor.map(support_matrix, all_ports_all_boards())))
 
     #print(json.dumps(boards, indent=2))
     return boards