SCons: Format buildsystem files with psf/black

Configured for a max line length of 120 characters.

psf/black is very opinionated and purposely doesn't leave much room for
configuration. The output is mostly OK so that should be fine for us,
but some things worth noting:

- Manually wrapped strings will be reflowed, so by using a line length
  of 120 for the sake of preserving readability for our long command
  calls, it also means that some manually wrapped strings are back on
  the same line and should be manually merged again.

- Code generators using string concatenation extensively look awful,
  since black puts each operand on a single line. We need to refactor
  these generators to use more pythonic string formatting, for which
  many options are available (`%`, `format` or f-strings).

- CI checks and a pre-commit hook will be added to ensure that future
  buildsystem changes are well-formatted.

(cherry picked from commit cd4e46ee65)

modules/mono/build_scripts/api_solution_build.py

@@ -8,21 +8,22 @@ from SCons.Script import Dir
 def build_api_solution(source, target, env):
     # source and target elements are of type SCons.Node.FS.File, hence why we convert them to str
 
-    module_dir = env['module_dir']
+    module_dir = env["module_dir"]
 
-    solution_path = os.path.join(module_dir, 'glue/GodotSharp/GodotSharp.sln')
+    solution_path = os.path.join(module_dir, "glue/GodotSharp/GodotSharp.sln")
 
-    build_config = env['solution_build_config']
+    build_config = env["solution_build_config"]
 
-    extra_msbuild_args = ['/p:NoWarn=1591']  # Ignore missing documentation warnings
+    extra_msbuild_args = ["/p:NoWarn=1591"]  # Ignore missing documentation warnings
 
     from .solution_builder import build_solution
+
     build_solution(env, solution_path, build_config, extra_msbuild_args=extra_msbuild_args)
 
     # Copy targets
 
-    core_src_dir = os.path.abspath(os.path.join(solution_path, os.pardir, 'GodotSharp', 'bin', build_config))
-    editor_src_dir = os.path.abspath(os.path.join(solution_path, os.pardir, 'GodotSharpEditor', 'bin', build_config))
+    core_src_dir = os.path.abspath(os.path.join(solution_path, os.pardir, "GodotSharp", "bin", build_config))
+    editor_src_dir = os.path.abspath(os.path.join(solution_path, os.pardir, "GodotSharpEditor", "bin", build_config))
 
     dst_dir = os.path.abspath(os.path.join(str(target[0]), os.pardir))
 
@@ -32,6 +33,7 @@ def build_api_solution(source, target, env):
 
     def copy_target(target_path):
         from shutil import copy
+
         filename = os.path.basename(target_path)
 
         src_path = os.path.join(core_src_dir, filename)
@@ -45,23 +47,28 @@ def build_api_solution(source, target, env):
 
 
 def build(env_mono):
-    assert env_mono['tools']
+    assert env_mono["tools"]
 
     target_filenames = [
-        'GodotSharp.dll', 'GodotSharp.pdb', 'GodotSharp.xml',
-        'GodotSharpEditor.dll', 'GodotSharpEditor.pdb', 'GodotSharpEditor.xml'
+        "GodotSharp.dll",
+        "GodotSharp.pdb",
+        "GodotSharp.xml",
+        "GodotSharpEditor.dll",
+        "GodotSharpEditor.pdb",
+        "GodotSharpEditor.xml",
     ]
 
     depend_cmd = []
 
-    for build_config in ['Debug', 'Release']:
-        output_dir = Dir('#bin').abspath
-        editor_api_dir = os.path.join(output_dir, 'GodotSharp', 'Api', build_config)
+    for build_config in ["Debug", "Release"]:
+        output_dir = Dir("#bin").abspath
+        editor_api_dir = os.path.join(output_dir, "GodotSharp", "Api", build_config)
 
         targets = [os.path.join(editor_api_dir, filename) for filename in target_filenames]
 
-        cmd = env_mono.CommandNoCache(targets, depend_cmd, build_api_solution,
-                                      module_dir=os.getcwd(), solution_build_config=build_config)
+        cmd = env_mono.CommandNoCache(
+            targets, depend_cmd, build_api_solution, module_dir=os.getcwd(), solution_build_config=build_config
+        )
         env_mono.AlwaysBuild(cmd)
 
         # Make the Release build of the API solution depend on the Debug build.