Rename 'Fuchsia Compile' to 'Fuchsia x64'

Infra side at https://chromium-review.googlesource.com/c/chromium/tools/build/+/721690.

TBR=scottmg@chromium.org

Bug: 758256
Change-Id: I236568f4bcd75f1106d017454fba5f5a950ef11a
Reviewed-on: https://chromium-review.googlesource.com/724620Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509667}

testing/buildbot/chromium.linux.json

@@ -3432,7 +3432,7 @@
       }
     ]
   },
-  "Fuchsia Compile": {
+  "Fuchsia x64": {
     "additional_compile_targets": [
       "base_unittests",
       "content_unittests",

testing/buildbot/chromium.sandbox.json

 {
-  "Fuchsia Compile SANDBOX": {
+  "Fuchsia x64 SANDBOX": {
     "additional_compile_targets": [
       "base_unittests",
       "content_unittests",

tools/mb/mb_config.pyl

@@ -320,7 +320,8 @@
       'Linux Builder (dbg)(32)': 'debug_bot_x86',
       'Linux Builder': 'release_bot',
       'Deterministic Linux': 'release_bot',
-      'Fuchsia Compile': 'release_bot_fuchsia',
+      'Fuchsia x64': 'release_bot_fuchsia',
+      'Fuchsia ARM64': 'release_bot_fuchsia_arm64',
     },
 
     'chromium.lkgr': {
@@ -392,7 +393,7 @@
     'chromium.sandbox': {
       'Linux Builder SANDBOX': 'release_bot',
       'Deterministic Linux SANDBOX': 'release_bot',
-      'Fuchsia Compile SANDBOX': 'release_bot_fuchsia',
+      'Fuchsia x64 SANDBOX': 'release_bot_fuchsia',
     },
 
     'chromium.swarm': {