perf: replace StringBuilder with ValueListBuilder<char>

[TimothyMakkison]

• Replaces StringBuilder with ValueListBuilder<char>
• Added some extension methods to make this easier
• Uses SkipLocalsInit to avoid the cost to zero stackalloc char[]

Benchmarks

I have no idea why, all the new changes I make are slower in the benchmarks, even when they should be a straight upgrade 🤔
I'm running into this issue a lot with #1542

Before

Method	Mean	Error	StdDev	Median	Gen0	Gen1	Allocated
Default_CodeFormatter_Tests	133.7 ms	2.65 ms	3.54 ms	133.7 ms	2000.0000	1000.0000	31.07 MB
Default_CodeFormatter_Complex	284.9 ms	5.60 ms	13.95 ms	279.1 ms	5000.0000	2000.0000	54.59 MB

After

Method	Mean	Error	StdDev	Median	Gen0	Gen1	Gen2	Allocated
Default_CodeFormatter_Tests	136.2 ms	2.69 ms	5.74 ms	134.5 ms	2000.0000	1000.0000	-	30.71 MB
Default_CodeFormatter_Complex	285.6 ms	5.71 ms	14.93 ms	278.1 ms	6000.0000	3000.0000	1000.0000	53.45 MB

[belav]

Did you figure out why your old benchmarks showed this as being slightly slower?

[TimothyMakkison]

In retrospect I think I was being overly paranoid. 😓 This is a net positive for memory usage with a negligible improvement to speed. The benchmarks naturally vary a little