Optimize & simplify Replace(char, char)

[Joy-less]

This PR does two things:

1. Simplifies & optimizes Replace(char, char). The built-in logic has low level optimizations on the buffer.
2. Optimizes ToValueStringBuilder(this StringBuilder) by passing setting the initial capacity to avoid growing the buffer.

They're one PR because I was too lazy to make two.

[Joy-less]

After benchmarking the optimization, I'm also reintroducing the optimization from my previous PR I closed:

Method	Mean	Error	StdDev	Gen0	Allocated
ReplaceChar	31.90 ns	0.189 ns	0.168 ns	0.0255	80 B
ReplaceString	38.85 ns	0.145 ns	0.121 ns	0.0255	80 B

This shows it's a good idea to simply use Replace(char, char) when the spans are of length 1.

[linkdotnet]

Give yourself some props in the changelog.

[Joy-less]

Give yourself some props in the changelog.

Done finally ^-^

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud