Add PGO documentation section to crate configuration (#18959)

Add section explaining Profile Guided Optimization can provide up to 25%
performance improvements. Includes three-stage build process
instructions and tips for effective PGO usage. References issue #9507.

## Which issue does this PR close?

Closes #9561 

## Rationale for this change

Adds documentation for Profile Guided Optimization (PGO) as requested.
PGO can provide up to 25% performance improvements for DataFusion
workloads, and users need clear guidance on how to use it.

## What changes are included in this PR?

- Added "Profile Guided Optimization (PGO)" section to
`docs/source/user-guide/crate-configuration.md`
- Three-stage build process instructions (instrumentation, profiling,
recompilation)
- Tips for effective PGO usage (representative workloads, multiple
iterations, combining with other optimizations)
- Links to Rust compiler guide and issue #9507

## Are these changes tested?

Yes. Documentation changes are validated by the CI workflow which builds
the docs and checks for errors. The markdown syntax is valid and follows
existing patterns.

## Are there any user-facing changes?

Yes. This adds documentation that will be published on the DataFusion
website under "Crate Configuration" > "Optimizing Builds". Users will
find guidance on using PGO to improve performance.

Author: jatinkumarsingh

docs/source/user-guide/crate-configuration.md

@@ -92,6 +92,36 @@ lto = true
 codegen-units = 1
 ```
 
+### Profile Guided Optimization (PGO)
+
+Profile Guided Optimization can improve DataFusion performance by up to 25%. It works by compiling with instrumentation, running representative workloads to collect profile data, then recompiling with optimizations based on that data.
+
+Build with instrumentation:
+
+```shell
+RUSTFLAGS="-C profile-generate=/tmp/pgo-data" cargo build --release
+```
+
+Run your workloads to collect profile data. Use benchmarks like TPCH or Clickbench, or your actual production queries:
+
+```shell
+./target/release/your-datafusion-app --benchmark
+```
+
+Rebuild using the collected profile:
+
+```shell
+RUSTFLAGS="-C profile-use=/tmp/pgo-data" cargo build --release
+```
+
+Tips:
+
+- Use workloads that match your production patterns
+- Run multiple iterations during profiling for better coverage
+- Combine with LTO and CPU-specific optimizations for best results
+
+See the [Rust compiler guide](https://rustc-dev-guide.rust-lang.org/building/optimized-build.html#profile-guided-optimization) for more details. Discussion and results in [issue #9507](https://github.com/apache/datafusion/issues/9507).
+
 ### Alternate Allocator: `snmalloc`
 
 You can also use [snmalloc-rs](https://crates.io/crates/snmalloc-rs) crate as