table: add more `noexcept`

Also merge fib-nexthop.hpp into fib-entry.hpp

Change-Id: Iec2fb90ede446f5b8d326c882904c70db45b87d6
diff --git a/daemon/table/pit-entry.hpp b/daemon/table/pit-entry.hpp
index a314ae6..321f5ea 100644
--- a/daemon/table/pit-entry.hpp
+++ b/daemon/table/pit-entry.hpp
@@ -275,7 +275,7 @@
    * \return an iterator to the in-record, or in_end() if it does not exist
    */
   InRecordCollection::iterator
-  findInRecord(const Face& face);
+  findInRecord(const Face& face) noexcept;
 
   /**
    * \brief Insert or update an in-record.
@@ -354,7 +354,7 @@
    * \return an iterator to the out-record, or out_end() if it does not exist
    */
   OutRecordCollection::iterator
-  findOutRecord(const Face& face);
+  findOutRecord(const Face& face) noexcept;
 
   /**
    * \brief Insert or update an out-record.