Blender Git Loki

Tests: performance testing framework

These are scripts for benchmarking Blender features on real-world .blend
files. They were originally written for benchmarking Cycles performance, and
were made generic so they can be used for more Blender features.

The benchmarks can be run locally by developers. But the plan is to also run
these as part of continuous integration to track performance over time.

Currently there are tests for Cycles rendering and .blend file loading.

Documentation:
https://wiki.blender.org/wiki/Tools/Tests/Performance

Main features:
* User created configurations to quickly run, re-run and analyze a selected
subset of tests.
* Supports both benchmarking with existing builds, and automatic building of
specified git commits, tags and branches.
* Generate HTML page with bar and line graphs from test results.
* Controlled using simple command line tool.
* For writing tests, convenient abstraction to run a Python function in Blender
with arguments and return value.

Ref T74730

Differential Revision: https://developer.blender.org/D11662