Choose logging backend on a per-target basis (project-chip#32119)

Executables and shared libraries now explicitly link with
`platform/logging:default` or `platform/logging:stdio`, so that the
`platform/logging:force_stdio` kludge is no longer needed.

The `chip_monolithic_tests` gn arg has been moved to `build/chip/tests.gni`.

Author: mbknust

build/chip/chip_test_suite.gni

@@ -94,9 +94,12 @@ template("chip_test_suite") {
 
     deps = [ dir_pw_unit_test ]
 
-    if (current_os != "zephyr" && current_os != "mbed") {
+    if (current_os != "zephyr" && current_os != "mbed" &&
+        chip_device_platform != "efr32") {
       # Depend on stdio logging, and have it take precedence over the default platform backend
-      public_deps += [ "${chip_root}/src/platform/logging:force_stdio" ]
+      public_deps += [ "${chip_root}/src/platform/logging:stdio" ]
+    } else {
+      public_deps += [ "${chip_root}/src/platform/logging:default" ]
     }
   }
   if (chip_link_tests) {

build/chip/tests.gni

@@ -18,6 +18,11 @@ import("//build_overrides/chip.gni")
 import("${chip_root}/build/chip/tools.gni")
 import("${chip_root}/src/platform/device.gni")
 
+declare_args() {
+  # Build monolithic test library.
+  chip_monolithic_tests = false
+}
+
 declare_args() {
   # Enable building tests.
   chip_build_tests = current_os != "freertos"