fboss2 bgp config: address clang-tidy findings

- Use auto for the SimpleJSONSerializer template-cast result in
  ConfigSession::saveBgpConfig() (modernize-use-auto).
- Drop redundant .c_str() on the TEnumTraits::findValue() argument in
  the neighbor enum attribute handler (readability-redundant-string-cstr).
- Drop the unused parseInt using-declaration in the peer-group
  dispatcher (misc-unused-using-decls).
- Drop the unused bgp_policy_types.h include from the as-path-list
  delete command (misc-include-cleaner).

Author: hillol-nexthop

fboss/cli/fboss2/commands/config/protocol/bgp/neighbor/CmdConfigProtocolBgpNeighbor.cpp

@@ -233,8 +233,7 @@ AttrHandler enumAttr(
       mode = static_cast<EnumT>(*enable ? 1 : 0);
       valid = true;
     } else {
-      valid = apache::thrift::TEnumTraits<EnumT>::findValue(
-          values[0].c_str(), &mode);
+      valid = apache::thrift::TEnumTraits<EnumT>::findValue(values[0], &mode);
     }
     if (!valid) {
       std::string names;

fboss/cli/fboss2/commands/config/protocol/bgp/peer-group/CmdConfigProtocolBgpPeerGroup.cpp

@@ -90,7 +90,6 @@ using PeerGroup = bgp::thrift::PeerGroup;
 using bgpcli::err;
 using bgpcli::ok;
 using bgpcli::parseBool;
-using bgpcli::parseInt;
 using bgpcli::parseNonNegInt32;
 using bgpcli::parseNonNegInt64;
 using bgpcli::Result;

fboss/cli/fboss2/commands/delete/protocol/bgp/policy/as-path-list/CmdDeleteProtocolBgpPolicyAsPathList.cpp

@@ -21,7 +21,6 @@
 #include <string>
 #include <utility>
 #include <vector>
-#include "configerator/structs/neteng/bgp_policy/thrift/gen-cpp2/bgp_policy_types.h"
 #include "fboss/cli/fboss2/session/ConfigSession.h"
 #include "fboss/cli/fboss2/utils/CmdUtilsCommon.h"
 #include "fboss/cli/fboss2/utils/HostInfo.h"

fboss/cli/fboss2/session/ConfigSession.cpp

@@ -592,7 +592,7 @@ void ConfigSession::saveBgpConfig() {
 
   // Serialize the entire typed config (round-tripped through parse so integer
   // map keys become string keys, mirroring saveConfig() for the agent).
-  std::string json =
+  auto json =
       apache::thrift::SimpleJSONSerializer::serialize<std::string>(bgpConfig_);
   std::string prettyJson = folly::toPrettyJson(folly::parseJson(json));
   folly::writeFileAtomic(