Use binary search in syscall defs

The lookup is not on the hot path and this removes the SYSCALLS_UNUSED macros.

PiperOrigin-RevId: 344240762
Change-Id: I324bd798945851ac0b92e257206525eab4ec36e5

sandboxed_api/sandbox2/BUILD.bazel

@@ -70,6 +70,7 @@ cc_library(
     deps = [
         ":config",
         ":util",
+        "@com_google_absl//absl/algorithm:container",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
         "@com_google_absl//absl/types:span",

sandboxed_api/sandbox2/CMakeLists.txt

@@ -64,7 +64,8 @@ add_library(sandbox2_syscall STATIC
 )
 add_library(sandbox2::syscall ALIAS sandbox2_syscall)
 target_link_libraries(sandbox2_syscall
-  PRIVATE absl::span
+  PRIVATE absl::algorithm_container
+          absl::span
           absl::str_format
           absl::strings
           sandbox2::util