Cleanup license metadata in external/rust/crates/fs-err.

Add package and license module in Android.bp. Symlink file LICENSE is added in Android codebase and points to file LICENSE-APACHE, so use it in Android.bp.

Bug: 346390141
Change-Id: Ic86a03ce73dbc127b2aea555e5ab10606863fe60
Test: CIs

Android.bp

diff --git a/Android.bp b/Android.bp
index ab2d598..fca35aa 100644
--- a/Android.bp
+++ b/Android.bp
@@ -3,7 +3,21 @@
 // because the changes will be overridden on upgrade.
 // Content before the first "rust_*" or "genrule" module is preserved.
 
-// TODO: Add license.
+package {
+    default_applicable_licenses: ["external_rust_crates_fs-err_license"],
+}
+
+license {
+    name: "external_rust_crates_fs-err_license",
+    visibility: [":__subpackages__"],
+    license_kinds: [
+        "SPDX-license-identifier-Apache-2.0",
+    ],
+    license_text: [
+        "LICENSE",
+    ],
+}
+
 rust_library {
     name: "libfs_err",
     host_supported: true,