Import YEEP-144 library 1.2 sources

Source-only snapshot of the 1.2 release. Drivers/ (the vendored ST HAL and
CMSIS) is excluded at 173 MB; fetch it from STMicroelectronics/STM32CubeH5 to
build.

.clangd

@@ -0,0 +1,11 @@
+CompileFlags:
+  Add:
+    - -ferror-limit=0
+    - -Wno-implicit-int
+  CompilationDatabase: build/Debug
+Diagnostics:
+  Suppress:
+    - unused-includes
+    - unknown_typename
+    - unknown_typename_suggest
+    - typename_requires_specqual