Fix regression to hardcoded AGP/Kotlin values in Android module templates (#160108)

https://github.com/flutter/flutter/pull/159770 regressed the module
templates to use a hardcoded `8.7.0` and `1.8.22` as the AGP and Kotlin
versions respectively. This PR returns them to using the template
context values.

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there for submitting PRs.
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we expect every widget to implement].
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- [ ] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
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Fixes] where supported.
- [ ] All existing and new tests are passing.

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---------

Co-authored-by: Gray Mackall <mackall@google.com>

packages/flutter_tools/templates/module/android/host_app_ephemeral/settings.gradle.tmpl

@@ -20,8 +20,8 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.library" version "8.7.0" apply false
-    id "org.jetbrains.kotlin.android" version "1.8.22" apply false
+    id "com.android.library" version "{{agpVersionForModule}}" apply false
+    id "org.jetbrains.kotlin.android" version "{{kotlinVersion}}" apply false
 }
 
 include ':app'

packages/flutter_tools/templates/template_manifest.json

@@ -164,7 +164,7 @@
         "templates/module/android/host_app_common/app.tmpl/src/main/res/mipmap-hdpi/ic_launcher.png",
         "templates/module/android/host_app_common/app.tmpl/src/main/res/values/styles.xml",
         "templates/module/android/host_app_editable/settings.gradle.copy.tmpl",
-        "templates/module/android/host_app_ephemeral/settings.gradle.copy.tmpl",
+        "templates/module/android/host_app_ephemeral/settings.gradle.tmpl",
         "templates/module/android/library/Flutter.tmpl/build.gradle.tmpl",
         "templates/module/android/library/Flutter.tmpl/flutter.iml.copy.tmpl",
         "templates/module/android/library/Flutter.tmpl/src/main/AndroidManifest.xml.tmpl",