[Remote signer] Fold signer into Lighthouse repository (#1852)

The remote signer relies on the `types` and `crypto/bls` crates from Lighthouse. Moreover, a number of tests of the remote signer consumption of LH leverages this very signer, making any important update a potential dependency nightmare.

Co-authored-by: Paul Hauner <paul@paulhauner.com>

remote_signer/tests/get_keys.rs

@@ -0,0 +1,84 @@
+mod get_keys {
+    use client::api_response::KeysApiResponse;
+    use helpers::*;
+
+    fn assert_ok(resp: ApiTestResponse, expected_keys_len: usize) {
+        assert_eq!(resp.status, 200);
+        assert_eq!(
+            serde_json::from_value::<KeysApiResponse>(resp.json)
+                .unwrap()
+                .keys
+                .len(),
+            expected_keys_len
+        );
+    }
+
+    fn assert_error(resp: ApiTestResponse, http_status: u16, error_msg: &str) {
+        assert_eq!(resp.status, http_status);
+        assert_eq!(resp.json["error"], error_msg);
+    }
+
+    #[test]
+    fn all_files_in_dir_are_public_keys() {
+        let (test_signer, tmp_dir) = set_up_api_test_signer_raw_dir();
+        add_key_files(&tmp_dir);
+
+        let url = format!("{}/keys", test_signer.address);
+
+        let resp = http_get(&url);
+        assert_ok(resp, 3);
+
+        test_signer.shutdown();
+    }
+
+    #[test]
+    fn some_files_in_dir_are_public_keys() {
+        let (test_signer, tmp_dir) = set_up_api_test_signer_raw_dir();
+        add_sub_dirs(&tmp_dir);
+        add_key_files(&tmp_dir);
+        add_non_key_files(&tmp_dir);
+
+        let url = format!("{}/keys", test_signer.address);
+
+        let resp = http_get(&url);
+        assert_ok(resp, 3);
+
+        test_signer.shutdown();
+    }
+
+    #[test]
+    fn no_files_in_dir_are_public_keys() {
+        let (test_signer, tmp_dir) = set_up_api_test_signer_raw_dir();
+        add_sub_dirs(&tmp_dir);
+        add_non_key_files(&tmp_dir);
+
+        let url = format!("{}/keys", test_signer.address);
+
+        let resp = http_get(&url);
+        assert_error(resp, 404, "No keys found in storage.");
+
+        test_signer.shutdown();
+    }
+
+    #[test]
+    fn directory_failure() {
+        let (test_signer, tmp_dir) = set_up_api_test_signer_raw_dir();
+        add_sub_dirs(&tmp_dir);
+        add_key_files(&tmp_dir);
+        add_non_key_files(&tmp_dir);
+
+        // Somebody tripped over a wire.
+        set_permissions(tmp_dir.path(), 0o40311);
+
+        let url = format!("{}/keys", test_signer.address);
+
+        let resp = http_get(&url);
+
+        // Be able to delete the tempdir afterward, regardless of this test result.
+        set_permissions(tmp_dir.path(), 0o40755);
+
+        assert_error(resp, 500, "Storage error: PermissionDenied");
+
+        test_signer.shutdown();
+    }
+}