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).
This extracts the sample code out from the API doc comments, and places them in separate files on disk, allowing running of the examples locally, testing them, and building of slightly larger examples.
