Revert "[ios] Drop iOS10 support, move deployment target to iOS11."

This reverts commit 7b97163e.

Reason for revert: Failed ios-device build 
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/ios-device/103715

Original change's description:
> [ios] Drop iOS10 support, move deployment target to iOS11.
> 
> Bug: 894099
> Change-Id: I638bd439a96e105cd33aa858cfd1209ed2ceabc9
> Reviewed-on: https://chromium-review.googlesource.com/c/1297250
> Reviewed-by: Justin Cohen <justincohen@chromium.org>
> Reviewed-by: Peter Lee <pkl@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Commit-Queue: Justin Cohen <justincohen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#603758}

TBR=dpranke@chromium.org,marq@chromium.org,justincohen@chromium.org,pkl@chromium.org,scottmg@chromium.org,jbudorick@chromium.org

Change-Id: Id78ea18cc5a77fa7a967867a890dd81a6af5eea6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 894099
Reviewed-on: https://chromium-review.googlesource.com/c/1306936Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603769}

build/config/ios/ios_sdk_overrides.gni

@@ -7,11 +7,11 @@
 
 declare_args() {
   # Version of iOS that we're targeting.
-  ios_deployment_target = "11.0"
+  ios_deployment_target = "10.0"
 }
 
 # Always assert that ios_deployment_target is used on non-iOS platforms to
 # prevent unused args warnings.
 if (!is_ios) {
-  assert(ios_deployment_target == "11.0" || true)
+  assert(ios_deployment_target == "10.0" || true)
 }

ios/build/bots/chromium.clang/ToTiOS.json

@@ -8,6 +8,7 @@
     "is_component_build=false",
     "is_debug=false",
     "llvm_force_head_revision=true",
+    "additional_target_cpus=[\"x86\"]",
     "target_cpu=\"x64\"",
     "target_os=\"ios\""
   ],

ios/build/bots/chromium.fyi/ios-simulator.json

@@ -4,6 +4,7 @@
   ],
   "xcode build version": "10a254a",
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "is_component_build=false",
     "is_debug=true",

ios/build/bots/chromium.fyi/ios12-beta-simulator.json

@@ -6,6 +6,7 @@
   "xcode build version": "10a254a",
   "gn_args": [
     "goma_dir=\"$(goma_dir)\"",
+    "additional_target_cpus=[\"x86\"]",
     "is_component_build=false",
     "is_debug=true",
     "symbol_level=1",

ios/build/bots/chromium.fyi/ios12-sdk-simulator.json

@@ -6,6 +6,7 @@
   ],
   "xcode build version": "10o45e",
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "is_component_build=false",
     "is_debug=true",

ios/build/bots/chromium.fyi/ios12-sdk-xcode-clang.json

@@ -7,6 +7,7 @@
   "xcode build version": "10a254a",
   "use xcode build version": true,
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "ios_enable_code_signing=false",
     "is_component_build=false",
     "is_debug=true",

ios/build/bots/chromium.mac/ios-simulator-full-configs.json

@@ -5,6 +5,7 @@
   ],
   "xcode build version": "10a254a",
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "is_component_build=false",
     "is_debug=true",

ios/build/bots/chromium.mac/ios-simulator-xcode-clang.json

@@ -7,6 +7,7 @@
   "xcode build version": "10a254a",
   "use xcode build version": true,
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "ios_enable_code_signing=false",
     "is_component_build=false",

ios/build/bots/chromium.mac/ios-simulator.json

@@ -6,6 +6,7 @@
   ],
   "xcode build version": "10a254a",
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "is_component_build=false",
     "is_debug=true",

ios/build/bots/chromium.mac/ios-uirefresh-simulator.json

@@ -5,6 +5,7 @@
   "xcode build version": "10a254a",
   "gn_args": [
     "goma_dir=\"$(goma_dir)\"",
+    "additional_target_cpus=[\"x86\"]",
     "is_component_build=false",
     "is_debug=true",
     "symbol_level=1",

ios/build/bots/chromium.mac/ios12-sdk-simulator.json

@@ -6,6 +6,7 @@
   ],
   "xcode build version": "10a254a",
   "gn_args": [
+    "additional_target_cpus=[\"x86\"]",
     "goma_dir=\"$(goma_dir)\"",
     "is_component_build=false",
     "is_debug=true",