docs: clarify prestateTracer behavior regarding code inclusion

[samuelarogbonlo]

This PR improves documentation to clarify the behavior of prestateTracer that was reported in issue #31794.

The prestateTracer captures full account state by default, including code, even when only specific fields like balance are accessed. This behavior is intentional but was not clearly documented. This PR:

1. Creates a TRACERS.md documentation file explaining prestateTracer behavior
2. Adds a simple test example in test/prestate-tracer-example demonstrating the behavior with and without the disableCode option

The PR does not change any functionality, only improves documentation to help users understand the expected behavior and how to use the disableCode option when they want to exclude code from the trace output.

Fixes #31794

[jsvisa]

I think our wiki page has already documented the prestate trace options, https://geth.ethereum.org/docs/developers/evm-tracing/built-in-tracers#prestate-tracer

[samuelarogbonlo]

I think our wiki page has already documented the prestate trace options, https://geth.ethereum.org/docs/developers/evm-tracing/built-in-tracers#prestate-tracer

Thank you for pointing this out! You're absolutely right - the official documentation at https://geth.ethereum.org/docs/developers/evm-tracing/built-in-tracers#prestate-tracer already covers this behavior comprehensively, including the disableCode option and examples.

I was not aware of this existing documentation when I created this PR. Since the information is already well-documented, I'll close this PR.

Thanks for the review and for pointing me to the existing documentation!