make all non hardware_ libraries foo add C preprocessor definition LIB_FOO=1, and remove bespoke definitions which were all undocumented anyway (#374)

src/rp2_common/pico_runtime/CMakeLists.txt

@@ -1,4 +1,4 @@
-add_library(pico_runtime INTERFACE)
+pico_add_impl_library(pico_runtime)
 
 target_sources(pico_runtime INTERFACE
         ${CMAKE_CURRENT_LIST_DIR}/runtime.c

src/rp2_common/pico_runtime/runtime.c

@@ -225,7 +225,7 @@ void __attribute__((noreturn)) panic_unsupported() {
 void __attribute__((noreturn)) __printflike(1, 0) panic(const char *fmt, ...) {
     puts("\n*** PANIC ***\n");
     if (fmt) {
-#if PICO_PRINTF_NONE
+#if LIB_PICO_PRINTF_NONE
         puts(fmt);
 #else
         va_list args;