[upstream_utils] Use pathlib instead of os.path (#7983)

A noteworthy change is the replacement of the `dp.startswith(os.path.join(".", "subdir"))` pattern. pathlib doesn't offer something with similar semantics besides `match` and `full_match`, so there's now a helper function that replicates the behavior.

Other notable changes include the addition of type annotations to ensure code correctness, using == to check file names instead of `endswith` for clarity (`endswith` is still used to check extensions), manual walking and copying being refactored in googletest, json, memory, nanopb, protobuf, and sleipnir to use `walk_cwd_and_copy_if`, and matching functions being shortened to the point where they can just be inlined into the lambda.

Co-authored-by: Tyler Veness <calcmogul@gmail.com>
Co-authored-by: David Vo <auscompgeek@users.noreply.github.com>

upstream_utils/stb.py

@@ -1,27 +1,27 @@
 #!/usr/bin/env python3
 
-import os
 import shutil
+from pathlib import Path
 
 from upstream_utils import Lib, walk_cwd_and_copy_if
 
 
-def copy_upstream_src(wpilib_root):
-    stb = os.path.join(wpilib_root, "thirdparty", "imgui_suite", "stb")
+def copy_upstream_src(wpilib_root: Path):
+    stb = wpilib_root / "thirdparty/imgui_suite/stb"
 
     # Delete old install
     for d in ["include", "cpp"]:
-        shutil.rmtree(os.path.join(stb, d), ignore_errors=True)
+        shutil.rmtree(stb / d, ignore_errors=True)
 
     # Copy files
-    files = walk_cwd_and_copy_if(
+    walk_cwd_and_copy_if(
         lambda dp, f: f == "stb_image.h",
-        os.path.join(stb, "include"),
+        stb / "include",
     )
 
-    os.makedirs(os.path.join(stb, "cpp"))
+    (stb / "cpp").mkdir(parents=True)
 
-    with open(os.path.join(stb, "cpp", "stb_image.cpp"), "w") as f:
+    with open(stb / "cpp/stb_image.cpp", "w") as f:
         f.write(
             """#define STBI_WINDOWS_UTF8
 #define STB_IMAGE_IMPLEMENTATION