Embedded resources management in JMeter

@pmouawad ([Bug 65890](https://bz.apache.org/bugzilla//show_bug.cgi?id=65890&redirect=false)):
1) It looks that today JMeter may not be good enough in this field:

As a recap, there are 2 options to simulate this today:

- Check "Embedded resources download" and Parallel in HTTP Request Advanced tab: JMeter will be realistic in the way it downloads resources but will download more or less resources compared to what a browser would do as it relies on parsing the HTML /CSS and extracting links

- Record including embedded resources (images, css, js) but during replay it will not be realistic. Using Parallel Controller or Parallel Sampler plugin will not be realistic either and this plugin has other bugs (sync issue on JMeter Variables...) and looks like it's not maintained anymore

Ideas to be enriched:

- During recording, record the list of downloaded resources and add them to the HTTP Request sampler and when checking embedded resource download, pick this list

2) Another problem is performance impact on JMeter of this feature.

OS: All