Re-sets two jvmargs that were getting cleared because we set a value for `-Xmx`. Could help with https://github.com/flutter/flutter/issues/142957. Copied from comment here https://github.com/flutter/flutter/issues/142957:
>Two random things I ran into while looking into this that might help:
>
>1. Gradle has defaults for a couple of the jvmargs, and setting any one of them clears those defaults for the others (bug here https://github.com/gradle/gradle/issues/19750). This can cause the "Gradle daemon to consume more and more native memory until it crashes", though the bug typically has a different associated error. It seems worth it to re-set those defaults.
>2. There is a property we can set that will give us a heap dump on OOM ([-XX:HeapDumpOnOutOfMemoryError](https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/clopts001.html))
Mostly just a find and replace from `find . -name gradle.properties -exec sed -i '' 's/\-Xmx4G/-Xmx4G\ \-XX:MaxMetaspaceSize=2G\ \-XX:+HeapDumpOnOutOfMemoryError/g' {} \;`, with the templates and the one test that writes from a string replaced by hand. I didn't set a value for `MaxMetaspaceSize` in the template files because I want to make sure this value doesn't cause problems in ci first (changes to the templates are essentially un-revertable for those who `flutter create` while the changes exist).
I updated the build files for manual_tests, as well as adding in a macos and web directory to allow the manual tests to be run on the web or on desktop.
The main change here are the parts that I added to the files in manual_tests/lib/... (the addition of kIsWeb to "if (!kIsWeb && Platform.isMacOS) {") The rest is just an update of the auto-generated code from flutter create.
