Benchmarks: added Go, abs2 in mandelbrot, moved plot to front page

[johnfgibson]

This PR

• Adds benchmark results from Go
• Switches to a uniform user-defined function abs2 within the mandelbrot benchmark and renames that userfunc_mandelbrot.
• Folds in revised results from a small range(t) fix in Python benchmarks JuliaLang/julia#24089
• Swaps the placement of the benchmark plot (now on front page) and table (now behind a link)
• Revises front-page text describing the aim of the benchmark, trying to highlight the focus on identical algorithms and code patterns instead of fastest method of computing the result.

[StefanKarpinski]

Can we get these without the </col> – browsers render them in the output? I made that change to Julia master already, so if you rebase your changes, the Perl script that generates this should not include these. Alternatively, you can just edit here.

[ViralBShah]

Are all the other benchmarks using abs2 uniformly. I only see the julia change in here, and am assuming that we may have needed it in other cases too.

[KristofferC]

The actual benchmark code is in the Julia repo though, right?

[johnfgibson]

@ViralBShah: I'm working on a PR to JuliaLang/julia with the change to abs2 and name userfunc_mandelbrot in all the benchmark codes, probably will file tomorrow.

[ViralBShah]

Thank you. Forgot for a moment that these are separate repos.

[ChrisRackauckas]

Anything blocking this?

[StefanKarpinski]

I wasn't sure if we should merge this before a PR exists for the corresponding code changes, but sure, no harm I guess.