Resolve Meson issues

This commit includes fixes in the repo:

1. Moving experimental filesystem to filesystem
2. Errors that meson identified

Signed-off-by: Ratan Gupta <ratankgupta31@gmail.com>
Change-Id: I93c77c2a434275c4da3ca4549919eaa55b57f481
diff --git a/snmp_serialize.hpp b/snmp_serialize.hpp
index 8f1400e..d5189a9 100644
--- a/snmp_serialize.hpp
+++ b/snmp_serialize.hpp
@@ -2,7 +2,7 @@
 
 #include "snmp_client.hpp"
 
-#include <experimental/filesystem>
+#include <filesystem>
 
 namespace phosphor
 {
@@ -13,7 +13,7 @@
 
 constexpr auto SEPARATOR = "_";
 
-namespace fs = std::experimental::filesystem;
+namespace fs = std::filesystem;
 
 /** @brief Serialize and persist SNMP manager/client D-Bus object.
  *  @param[in] id - filename of the persisted SNMP manager object.