Params: add new method to get all keys (#25779)

* allKeys

* cleanup and test

Co-authored-by: Adeeb Shihadeh <adeebshihadeh@gmail.com>
old-commit-hash: 85b433760a2c1a139062a40040e096b9de880e33

common/params.cc

@@ -3,6 +3,7 @@
 #include <dirent.h>
 #include <sys/file.h>
 
+#include <algorithm>
 #include <csignal>
 #include <unordered_map>
 
@@ -203,6 +204,14 @@ Params::Params(const std::string &path) {
   params_path = path.empty() ? default_param_path : ensure_params_path(prefix, path);
 }
 
+std::vector<std::string> Params::allKeys() const {
+  std::vector<std::string> ret;
+  for (auto &p : keys) {
+    ret.push_back(p.first);
+  }
+  return ret;
+}
+
 bool Params::checkKey(const std::string &key) {
   return keys.find(key) != keys.end();
 }