Restore php-xhprof and add php-excimer

Krinklerequested to merge
krinkle/dev-images:excimer-and-xhprof into main

Folllows-up efbc9504 (T338208), which changed the way xdebug was installed but accidentally removed the php-tideways-xhprof package that for some reason was installed from the same shell script.

Restore this and replace it with a simple apt-get for php-xhprof, which is conveniently packaged by deb.sury.org.

While at it, also add php-excimer so that it easier for people to generate flame graphs locally. Currently, this has to be installed out of bound (per 1 and 2), but this is lost the next time you docker composer up --build. Unless you use Excimer the same day, you're likely to forget during the next profiling attempt why this has suddenly stopped working, and lots of people waste time debugging again only to re-discover the same cause and re-install yet again.

Bug: T401115

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