[Perf] Display results with 4 significant figures

[mikeharder]

Before

Completed 4,007 operations in a weighted-average of 10.04s (399.13 ops/s, 0.003 s/op)

Test	Arguments	12.13.0	source	%Change
download	--size 10240 --parallel 64	409.48	402.01	-1.82%
download	--size 10485760 --parallel 32	45.28	43.96	-2.92%
download	--size 1073741824 --parallel 1 --warmup 60 --duration 60	0.14	0.14	0.00%
download	--size 1073741824 --parallel 8 --warmup 60 --duration 60	0.39	0.39	0.00%

After

Completed 4,003 operations in a weighted-average of 10.04s (398.8 ops/s, 0.002507 s/op)

Test	Arguments	12.13.0	source	%Change
download	--size 10240 --parallel 64	405.4	402.3	-0.76%
download	--size 10485760 --parallel 32	45.88	45.83	-0.11%
download	--size 1073741824 --parallel 1 --warmup 60 --duration 60	0.1271	0.1264	-0.55%
download	--size 1073741824 --parallel 8 --warmup 60 --duration 60	0.4177	0.3913	-6.32%

Validation Build

https://dev.azure.com/azure-sdk/internal/_build/results?buildId=1743985&view=results