Convert team_number to use string_view

Remove StringToNumber while we are here since it has been replaced by
absl and is used in exactly 1 spot.

Change-Id: Idfdb7876208608819b855c42f930a7a10ada3855
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/network/team_number.h b/aos/network/team_number.h
index c2954b6..8effc27 100644
--- a/aos/network/team_number.h
+++ b/aos/network/team_number.h
@@ -4,7 +4,7 @@
 #include <stdint.h>
 
 #include <optional>
-#include <string>
+#include <string_view>
 
 #include "glog/logging.h"
 
@@ -29,14 +29,14 @@
 void OverrideTeamNumber(uint16_t team);
 
 // Returns the pi number for a pi formated hostname.  pi-team#-pi# (pi-971-5)
-std::optional<uint16_t> ParsePiNumber(const std::string &hostname);
+std::optional<uint16_t> ParsePiNumber(const std::string_view hostname);
 
 namespace team_number_internal {
 
-std::optional<uint16_t> ParseRoborioTeamNumber(const std::string &hostname);
+std::optional<uint16_t> ParseRoborioTeamNumber(const std::string_view hostname);
 
 // Returns the team number for a pi formated hostname.  pi-team#-pi#
-std::optional<uint16_t> ParsePiTeamNumber(const std::string &hostname);
+std::optional<uint16_t> ParsePiTeamNumber(const std::string_view hostname);
 
 }  // namespace team_number_internal
 }  // namespace network