[build] Move the version provider to tool.dynamic-metadata

[aaronj0]

Fixes the installation warning:

2026-08-20T11:54:26.9411113Z   Preparing metadata (pyproject.toml): started
2026-08-20T11:54:26.9411738Z   Running command Preparing metadata (pyproject.toml)
2026-08-20T11:54:27.2998517Z   WARNING: tool.scikit-build.metadata is deprecated; use the standard top-level [[tool.dynamic-metadata]] instead
2026-08-20T11:54:27.3027613Z   *** scikit-build-core 1.0.3 using CMake 3.31.6 (metadata_wheel)
2026-08-20T11:54:27.3745619Z   Preparing metadata (pyproject.toml): finished with status 'done'
2026-08-20T11:54:27.3766823Z Building wheels for collected packages: cppjit

[github-actions]

Test Results

Configuration	Result
macos-26-intel-llvm21-py3.14-cxx20	= 437 passed, 44 skipped, 85 xfailed, 32 xpassed, 100 warnings in 117.07s (0:01:57) =
macos-26-llvm21-py3.14-cxx20	==== 438 passed, 37 skipped, 93 xfailed, 30 xpassed, 100 warnings in 52.35s ====
ubuntu-24.04-llvm21-py3.14-cxx20-vg	====== 553 passed, 25 skipped, 18 xfailed, 2 xpassed in 94.16s (0:01:34) =======
ubuntu-24.04-llvm22-py3.14-cxx20	====== 553 passed, 25 skipped, 19 xfailed, 1 xpassed in 102.77s (0:01:42) ======
ubuntu-24.04-llvm22-py3.14-cxx20-cling	====== 543 passed, 25 skipped, 27 xfailed, 3 xpassed in 109.97s (0:01:49) ======
ubuntu-24.04-llvm22-py3.14-cxx23	======= 574 passed, 3 skipped, 20 xfailed, 1 xpassed in 80.06s (0:01:20) =======