Enable extra build dependencies to 'match runtime' versions (#15036)

## Summary

This is an alternative to https://github.com/astral-sh/uv/pull/14944
that functions a little differently. Rather than adding separate
strategies, you can instead say:

```toml
[tool.uv.extra-build-dependencies]
child = [{ requirement = "anyio", match-runtime = true }]
```

Which will then enforce that `anyio` uses the same version as in the
lockfile.

uv.schema.json

@@ -889,10 +889,32 @@
       "additionalProperties": {
         "type": "array",
         "items": {
-          "$ref": "#/definitions/Requirement"
+          "$ref": "#/definitions/ExtraBuildDependency"
         }
       }
     },
+    "ExtraBuildDependency": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/Requirement"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "match-runtime": {
+              "type": "boolean"
+            },
+            "requirement": {
+              "$ref": "#/definitions/Requirement"
+            }
+          },
+          "required": [
+            "requirement",
+            "match-runtime"
+          ]
+        }
+      ]
+    },
     "ExtraName": {
       "description": "The normalized name of an extra dependency.\n\nConverts the name to lowercase and collapses runs of `-`, `_`, and `.` down to a single `-`.\nFor example, `---`, `.`, and `__` are all converted to a single `-`.\n\nSee:\n- <https://peps.python.org/pep-0685/#specification/>\n- <https://packaging.python.org/en/latest/specifications/name-normalization/>",
       "type": "string"