Add xdsl constant folding benchmark

[EdmundGoodman]

As discussed in the xDSL Zulip, this PR adds a benchmark for constant folding with xDSL.

The new benchmark appears to run as expected locally:

$ pyperformance run --benchmark xdsl                                                                                         
Python benchmark suite 1.11.0


==================================================
( 1/1) creating venv for benchmark (xdsl)

(trying common venv first)
Installing requirements into the virtual environment /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b
# /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/bin/python -m pip install xdsl==0.46.0 pyperf==2.9.0
Requirement already satisfied: xdsl==0.46.0 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (0.46.0)
Requirement already satisfied: pyperf==2.9.0 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (2.9.0)
Requirement already satisfied: immutabledict<4.2.2 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (from xdsl==0.46.0) (4.2.1)
Requirement already satisfied: typing-extensions<5,>=4.7 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (from xdsl==0.46.0) (4.14.1)
Requirement already satisfied: ordered-set==4.1.0 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (from xdsl==0.46.0) (4.1.0)
Requirement already satisfied: psutil>=5.9.0 in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (from pyperf==2.9.0) (7.0.0)

[notice] A new release of pip is available: 24.3.1 -> 25.1.1
[notice] To update, run: python -m pip install --upgrade pip
Installing requirements into the virtual environment /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b
# /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/bin/python -m pip install psutil
Requirement already satisfied: psutil in ./venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/lib/python3.12/site-packages (7.0.0)

[notice] A new release of pip is available: 24.3.1 -> 25.1.1
[notice] To update, run: python -m pip install --upgrade pip
# /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/bin/python -m pip freeze
immutabledict==4.2.1
ordered-set==4.1.0
psutil==7.0.0
pyperf==2.9.0
setuptools==80.9.0
typing_extensions==4.14.1
wheel==0.45.1
xdsl==0.46.0
# /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/bin/python -m pip freeze
immutabledict==4.2.1
ordered-set==4.1.0
psutil==7.0.0
pyperf==2.9.0
setuptools==80.9.0
typing_extensions==4.14.1
wheel==0.45.1
xdsl==0.46.0

[1/1] xdsl...
# /Users/edjg/.../pyperformance/venv/cpython3.12-30629e8c4b43-compat-64aaec271e6b/bin/python -u /Users/edjg/.../pyperformance/pyperformance/data-files/benchmarks/bm_xdsl/run_benchmark.py --output /var/folders/dw/qzkqk1s50cd9stxcw22_ymj80000gn/T/tmp4lrfn0vn --inherit-environ PYPERFORMANCE_RUNID
.....................
WARNING: the benchmark result may be unstable
* Not enough samples to get a stable result (95% certainly of less than 1% variation)

Try to rerun the benchmark with more runs, values and/or loops.
Run 'python -m pyperf system tune' command to reduce the system jitter.
Use pyperf stats, pyperf dump and pyperf hist to analyze results.
Use --quiet option to hide these warnings.

xdsl_constant_fold: Mean +- std dev: 24.3 ms +- 1.0 ms

Performance version: 1.11.0
Python version: 3.12.9 (64-bit)
Report on macOS-15.5-arm64-arm-64bit
Number of logical CPUs: 8
Start date: 2025-07-23 12:32:57.663942
End date: 2025-07-23 12:33:18.527806

### xdsl_constant_fold ###
Mean +- std dev: 24.3 ms +- 1.0 ms

[Fidget-Spinner]

Do we need to specify an xdsl version here? I forgot how pyproject.toml specifications work. Presumably yes?

[EdmundGoodman]

Moved to PR main repo here: python#403