Add progress logging based on ProgressLogging.jl spec

[tkf]

With this patch, BenchmarkTools now emits progress logging records as specified by ProgressLogging.jl. You can observe progress as progress bars if you set up a progress monitor such as Juno and TerminalLoggers.jl

Note that this patch does not add ProgressLogging.jl or any non-stdlib packages as dependencies.

Example:

using Logging
using TerminalLoggers
using BenchmarkTools

with_logger(TerminalLogger()) do
    suite = BenchmarkGroup()
    for n in [100, 200, 400]
        suite[n] = s1 = BenchmarkGroup()
        for T in [Int, Float64, ComplexF64]
            s1[T] = @benchmarkable rand($T, $n)
        end
    end
    tune!(suite, verbose=true)
    run(suite, verbose=true)
end