[vm] Use fuchsia.deprecatedtimezone

This sets us up for migrating away from a dedicated timezone service
into a more general `fuchsia.intl.*`.

As a first step, let's use only one of the two equivalent FIDL service sets.
In fuchsia they are implemented by exactly the same handlers, so are equivalent
to the best of my knowledge.

Fixes #39174.

Change-Id: I229670bb96816af808a0cb14e6d2cba283f9ef62
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/123487
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

Author: filmil

runtime/vm/BUILD.gn

@@ -79,7 +79,7 @@ library_for_all_configs("libdart_vm") {
         # TODO(US-399): Remove time_service specific code when it is no longer
         # necessary.
         "//sdk/lib/sys/cpp",
-        "//sdk/fidl/fuchsia.timezone",
+        "//sdk/fidl/fuchsia.deprecatedtimezone",
 
         "//zircon/public/lib/fbl",
         "//zircon/public/lib/trace-engine",

runtime/vm/os_fuchsia.cc

@@ -8,14 +8,7 @@
 #include "vm/os.h"
 
 #include <errno.h>
-#if defined(FUCHSIA_SDK)
 #include <fuchsia/deprecatedtimezone/cpp/fidl.h>
-namespace fuchsia {
-namespace timezone = deprecatedtimezone;
-}
-#else
-#include <fuchsia/timezone/cpp/fidl.h>
-#endif  //  defined(FUCHSIA_SDK)
 #include <lib/sys/cpp/service_directory.h>
 #include <zircon/process.h>
 #include <zircon/syscalls.h>
@@ -50,7 +43,7 @@ intptr_t OS::ProcessId() {
 // Putting this hack right now due to CP-120 as I need to remove
 // component:ConnectToEnvironmentServices and this is the only thing that is
 // blocking it and FL-98 will take time.
-static fuchsia::timezone::TimezoneSyncPtr tz;
+static fuchsia::deprecatedtimezone::TimezoneSyncPtr tz;
 
 static zx_status_t GetLocalAndDstOffsetInSeconds(int64_t seconds_since_epoch,
                                                  int32_t* local_offset,