Add new ANGLE Linux and Mac tester configs.

These configs will replace linux_angle_rel_ng and mac_angle_rel_ng.
They initially mirror the configuration but will soon be updated to
run only the subsets of tests that are most relevant to ANGLE. This
should reduce flakiness in ANGLE and reduce load for Chrome.

Also updates related configuration files to include linux-angle-rel
and mac-angle-rel.

Bug: 822310
Change-Id: I2b40ed45f5d9e105c088ab166bd2207c96280151
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1551463
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#647854}

infra/config/cr-buildbucket.cfg

@@ -3387,6 +3387,7 @@ buckets {
       name: "gpu-manual-try-linux-nvidia-tsn"
     }
     builders { mixins: "linux-try" name: "leak_detection_linux" }
+    builders { mixins: "linux-angle-try" name: "linux-angle-rel" }
     builders { mixins: "linux-angle-try" name: "linux_angle_compile_dbg_ng" }
     builders { mixins: "linux-angle-try" name: "linux_angle_dbg_ng" }
     builders { mixins: "linux-angle-try" name: "linux_angle_deqp_rel_ng" }
@@ -3506,6 +3507,7 @@ buckets {
     builders { mixins: "ios-try" name: "ios-simulator-eg" }
     builders { mixins: "ios-try" name: "ios-simulator-xcode-clang" }
     builders { mixins: "ios-try" name: "ios-slimnav" }
+    builders { mixins: "mac-angle-try" name: "mac-angle-rel" }
     builders { mixins: "mac-angle-try" name: "mac_angle_compile_dbg_ng" }
     builders { mixins: "mac-angle-try" name: "mac_angle_dbg_ng" }
     builders { mixins: "mac-angle-try" name: "mac_angle_rel_ng" }

infra/config/luci-milo.cfg

@@ -4368,6 +4368,9 @@ consoles {
   builders {
     name: "buildbucket/luci.chromium.try/android_angle_vk64_rel_ng"
   }
+  builders {
+    name: "buildbucket/luci.chromium.try/linux-angle-rel"
+  }
   builders {
     name: "buildbucket/luci.chromium.try/linux_angle_dbg_ng"
   }
@@ -4380,6 +4383,9 @@ consoles {
   builders {
     name: "buildbucket/luci.chromium.try/linux_angle_rel_ng"
   }
+  builders {
+    name: "buildbucket/luci.chromium.try/mac-angle-rel"
+  }
   builders {
     name: "buildbucket/luci.chromium.try/mac_angle_dbg_ng"
   }
@@ -4609,6 +4615,9 @@ consoles {
   builders {
     name: "buildbucket/luci.chromium.try/gpu-manual-try-win10-nvidia-rel"
   }
+  builders {
+    name: "buildbucket/luci.chromium.try/linux-angle-rel"
+  }
   builders {
     name: "buildbucket/luci.chromium.try/linux-blink-heap-concurrent-marking-tsan-rel"
   }
@@ -4748,6 +4757,9 @@ consoles {
   builders {
     name: "buildbucket/luci.chromium.try/ios12-sdk-simulator"
   }
+  builders {
+    name: "buildbucket/luci.chromium.try/mac-angle-rel"
+  }
   builders {
     name: "buildbucket/luci.chromium.try/mac-jumbo-rel"
   }