Micro-optimisations: Improve memory usage for ReplaceMany string extension method

[patrickdemooij9]

Prerequisites

• I have added steps to test this contribution in the description below (Added extra unit test case & existing unit tests are succeeding)

Description

The old ReplaceMany was using multiple .Replace() functions, each of them creating a new string in memory. As it's just a char for char replacement, we can change this by constructing a single string and replacing them as we are constructing the string resulting in only one string being allocated.

I also reran all the benchmarks for the ReplaceMany and updated the timings (which also shows DotNet is just a lot faster in general :P). Main ones regarding this code are:

short text, short replacement:

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
'String.ReplaceMany w/chars - Aggregate'	68.65 ns	46.32 ns	2.539 ns	1.00	0.04	0.0185	240 B	1.00
'String.ReplaceMany w/chars - For Loop'	66.85 ns	10.66 ns	0.584 ns	0.97	0.03	0.0190	240 B	1.00
'String.ReplaceMany w/chars - String Create'	39.22 ns	13.80 ns	0.757 ns	0.57	0.02	0.0037	48 B	0.20

long text, short replacement:

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
'String.ReplaceMany w/chars - Aggregate'	426.0 ns	856.13 ns	46.93 ns	1.01	0.14	0.5656	6.97 KB	1.00
'String.ReplaceMany w/chars - For Loop'	415.0 ns	230.56 ns	12.64 ns	0.98	0.10	0.5658	6.97 KB	1.00
'String.ReplaceMany w/chars - String Create'	389.8 ns	177.93 ns	9.75 ns	0.92	0.09	0.1401	1.74 KB	0.25

[github-actions]

Hi there @patrickdemooij9, thank you for this contribution! 👍

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[AndyButland]

Thanks for this @patrickdemooij9 - looks good and worth having. I've just pushed an update with an increase in test coverage, and verified them on the before and after code.

[AndyButland]

Cherry-picked to v17/dev.