Add explanation about new optimization simpleCounterForLoopUncheckedIncrement

[matheusaaguiar]

Page

Optimizer Section of the documentation.

https://docs.soliditylang.org/en/latest/internals/optimizer.html

Abstract

Since 0.8.22, the compiler can use unchecked arithmetic when incrementing the counter of for loops, under certain specific conditions. Those conditions need to be properly explained in the documentation.
The blog post about the 0.8.22 release and the PR that introduced the functionality have the necessary information and examples about that.

[ekpyron]

This will in fact open a third subsection there besides Opcode-Based Optimizer Module and Yul-Based Optimizer Module.
As a name for that section, I'd suggest Codegen-Based Optimizations or Optimized Code Generation or such, but open for better choices (Code Generation Optimizations Based On An Analysis Of Solidity Code is a bit bulky :-)).

[matheusaaguiar]

Closed by #14650.