Add build and test configs for blimp client and engine bots on chromium.fyi.

build/args/bots/chromium.fyi/blimp_engine_rel.gn

Index: build/args/bots/chromium.fyi/blimp_engine_rel.gn
diff --git a/build/args/bots/chromium.fyi/blimp_engine_rel.gn b/build/args/bots/chromium.fyi/blimp_engine_rel.gn
new file mode 100644
index 0000000000000000000000000000000000000000..7a8261a06f5ed4057ec89a62e514abd26cd3dd69
--- /dev/null
+++ b/build/args/bots/chromium.fyi/blimp_engine_rel.gn
@@ -0,0 +1,11 @@
+import("//build/args/blimp_engine.gn")
+
+# release + official + DCHECKs is a weird combination of arguments!
+# However, it's an attempt to both:
+#  - emulate how the engine will be deployed
+#  - catch as many errors as possible
+# If it proves to be less than entirely stable, drop official and just do
+# release + DCHECKs
+is_debug = false
+is_official_build = true
+dcheck_always_on = true