Move flutter_*_runner to /system/bin (flutter#4286)

Previously, these binaries were in /system/apps, which is going away. Also,
rename flutter_runner to flutter_jit_runner to match flutter_aot_runner.

BUILD.gn

@@ -64,7 +64,6 @@ if (is_fuchsia) {
   import("//packages/package.gni")
 
   package("package") {
-    app = true
     testonly = true
 
     package_name = "flutter"
@@ -75,7 +74,7 @@ if (is_fuchsia) {
 
     binaries = [
       {
-        name = "flutter_runner"
+        name = "flutter_jit_runner"
       },
       {
         name = "flutter_aot_runner"

build/flutter_app.gni

@@ -166,7 +166,7 @@ template("flutter_jit_app") {
       "--depfile",
       rebase_path(bundle_depfile),
       "--interpreter",
-      "flutter_runner",
+      "flutter_jit_runner",
     ]
     if (defined(invoker.manifest)) {
       args += [

content_handler/BUILD.gn

@@ -87,7 +87,7 @@ template("flutter_content_handler") {
 }
 
 flutter_content_handler("content_handler") {
-  output_name = "flutter_runner"
+  output_name = "flutter_jit_runner"
   extra_deps = [ "//third_party/dart/runtime:libdart_jit" ]
 }