Install Tideways and XHGUI on Pull Request Tugboat Sandboxes

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Description of the need

During Backdrop LIVE March 12, @hosef gave a presentation on performance (notes available here on Google Docs), in which he details the use of Tideways and XHGUI

Although we could not devise a way to provide automated before/after performance testing in a way that would be useful without knowledge of how to use performance profiling software, we thought that the setup of the profiling software is the most difficult part of profiling.

Proposed solution

We could install Tideways and XHGUI in the Tugboat sandboxes to make it so that anyone could access profiling software on our sandboxes.

Alternatives that have been considered

Software like https://www.blackfire.io/ or New Relic could be used, but as far as we know, it's not possible to allow public access to the profile data, you must log into the corresponding service first.

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