Fix bug with imports field from a nested directory (#5366)

### Description

When importing a `#foo` subpath import, the resolved file is relative
the the `package.json` containing the `imports` field, not the file with
the import statement. This fixes subpath imports to use the proper
context path during that resolve.

### Testing Instructions

```
RUST_BACKTRACE=1 cargo nextest run -p turbopack-tests -E 'test(snapshot__imports__subpath_imports_nested)' --no-capture
```

Fixes WEB-1216

crates/turbopack-core/src/resolve/mod.rs

@@ -1343,7 +1343,7 @@ async fn resolve_package_internal_with_imports_field(
     };
 
     handle_exports_imports_field(
-        context,
+        package_json_path.parent(),
         *package_json_path,
         resolve_options,
         imports,

crates/turbopack-tests/tests/snapshot/imports/subpath-imports-nested/input/foo.js

@@ -0,0 +1 @@
+export default "foo";

crates/turbopack-tests/tests/snapshot/imports/subpath-imports-nested/input/index.js

@@ -0,0 +1,3 @@
+import foo from "./nested";
+
+console.log(foo);

crates/turbopack-tests/tests/snapshot/imports/subpath-imports-nested/input/nested/index.js

@@ -0,0 +1,2 @@
+import foo from "#foo";
+export default foo;

crates/turbopack-tests/tests/snapshot/imports/subpath-imports-nested/input/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "subpath-imports",
+  "imports": {
+    "#foo": "./foo.js"
+  }
+}