Implement event-based file upload

Delegate implementation and unittests are provided for ChromeOS Ash
only. Currently metadata and access are temporary placeholders, need to
be finalized.

Manually tested on VM.

Positive unit tests coverage is complete, negative tests are provided
for initialization, need to be added for next-step and finalization.

Bug: b:264399295
Change-Id: I9ba990a09aec125d725eba4233f1061767701935
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4336709
Reviewed-by: Vignesh Shenvi <vshenvi@google.com>
Commit-Queue: Leonid Baraz <lbaraz@chromium.org>
Reviewed-by: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Auto-Submit: Leonid Baraz <lbaraz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118797}

chrome/browser/BUILD.gn

@@ -1189,8 +1189,6 @@ static_library("browser") {
     "policy/messaging_layer/upload/encrypted_reporting_client.h",
     "policy/messaging_layer/upload/event_upload_size_controller.cc",
     "policy/messaging_layer/upload/event_upload_size_controller.h",
-    "policy/messaging_layer/upload/file_upload_impl.cc",
-    "policy/messaging_layer/upload/file_upload_impl.h",
     "policy/messaging_layer/upload/file_upload_job.cc",
     "policy/messaging_layer/upload/file_upload_job.h",
     "policy/messaging_layer/upload/network_condition_service.cc",
@@ -4887,6 +4885,8 @@ static_library("browser") {
       "platform_util_ash.cc",
       "policy/default_geolocation_policy_handler.cc",
       "policy/default_geolocation_policy_handler.h",
+      "policy/messaging_layer/upload/file_upload_impl.cc",
+      "policy/messaging_layer/upload/file_upload_impl.h",
       "policy/os_color_mode_policy_handler.cc",
       "policy/os_color_mode_policy_handler.h",
       "policy/status_provider/device_active_directory_policy_status_provider.cc",