fix(uavcan): silence DroneCAN DSDL compiler build warnings (#26757)

Fix Python DeprecationWarning for invalid escape sequence in pyratemp.py
and replace deprecated FindPythonInterp CMake module in libuavcan.

src/drivers/uavcan/libdronecan/libuavcan/CMakeLists.txt

@@ -21,7 +21,10 @@ endif ()
 
 project(libuavcan)
 
-find_package(PythonInterp)
+if(NOT PYTHON_EXECUTABLE)
+    find_package(Python3 COMPONENTS Interpreter)
+    set(PYTHON_EXECUTABLE ${Python3_EXECUTABLE})
+endif()
 
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
     set(COMPILER_IS_GCC_COMPATIBLE 1)

src/drivers/uavcan/libdronecan/libuavcan/dsdl_compiler/libuavcan_dsdl_compiler/pyratemp.py

@@ -278,7 +278,7 @@ def escape(s, format=HTML):
 
           - `NONE`:  nothing is replaced
           - `HTML`:  replace &<>'" by &...;
-          - `LATEX`: replace \#$%&_{}~^
+          - `LATEX`: replace \\#$%&_{}~^
           - `MAIL_HEADER`: escape non-ASCII mail-header-contents
     :Returns:
         the escaped string in unicode