Add support for config_settings in PEP 517 hooks (#1833)

## Summary

Adds `--config-setting` / `-C` (with a `--config-settings` alias for
convenience) to the CLI.

Closes https://github.com/astral-sh/uv/issues/1460.

scripts/editable-installs/setuptools_editable/.gitignore

@@ -0,0 +1,2 @@
+# Artifacts from the build process.
+*.egg-info/

scripts/editable-installs/setuptools_editable/pyproject.toml

@@ -0,0 +1,13 @@
+[project]
+name = "setuptools_editable"
+version = "0.1.0"
+description = "Default template for a setuptools project"
+authors = [
+    {name = "konstin", email = "konstin@mailbox.org"},
+]
+dependencies = ["iniconfig"]
+requires-python = ">=3.11,<3.13"
+license = {text = "MIT"}
+
+[project.optional-dependencies]
+anyio = ["anyio>=3.3.0"]

scripts/editable-installs/setuptools_editable/setuptools_editable/__init__.py

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+def a():
+    pass