Document Automatically Defined Compiler Symbols in F# Compiler Directives

[shethaadit]

PR Description:

This PR enhances the F# Compiler Directives documentation by adding a section on automatically defined symbols, such as DEBUG and TRACE. These symbols are implicitly defined by the compiler in specific build configurations and can be used for conditional compilation.

Changes Made:

• Added a new "Automatically Defined Symbols" section under Conditional Compilation Directives.
• Documented DEBUG (enabled in Debug builds) and TRACE (enabled in tracing configurations).
• Included a code example demonstrating conditional compilation using #if DEBUG.

This update helps developers understand which symbols are pre-defined by the F# compiler and how to use them effectively.

Fixes #45478

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Internal previews

📄 File	🔗 Preview link
docs/fsharp/language-reference/compiler-directives.md	Compiler Directives

[shethaadit]

Hi @BillWagner, @T-Gro, could you please review?

[BillWagner]

I'm generally OK with this one. I'd like @T-Gro to take a look before I merge.

[BillWagner]

@shethaadit Can you update based on @T-Gro 's comments?

[BillWagner]

@shethaadit Are you planning to update per @T-Gro 's comments?

[BillWagner]

Closing due to lack of response.