Implement SpanEqual and SpanHash

We desire the ability to hash and check equality of data across spans to use associative containers such as `std::unordered_map` with spans. The implemented functions provide an easy way to do that.

app/src/main/cpp/skyline/common/span.h

@@ -155,4 +155,26 @@ namespace skyline {
     span(Container &) -> span<typename Container::value_type>;
     template<typename Container>
     span(const Container &) -> span<const typename Container::value_type>;
+
+    /**
+     * @return If the contents of the two spans are byte-for-byte equal
+     */
+    template<typename T, size_t Extent = std::dynamic_extent>
+    struct SpanEqual {
+        constexpr bool operator()(const span<T, Extent> &lhs, const span<T, Extent> &rhs) const {
+            if (lhs.size_bytes() != rhs.size_bytes())
+                return false;
+            return std::equal(lhs.begin(), lhs.end(), rhs.begin());
+        }
+    };
+
+    /**
+     * @return A hash of the contents of the span
+     */
+    template<typename T, size_t Extent = std::dynamic_extent>
+    struct SpanHash {
+        constexpr size_t operator()(const skyline::span<T, Extent> &x) const {
+            return XXH64(x.data(), x.size_bytes(), 0);
+        }
+    };
 }