Bug 1957791 - Apply mozilla patches for opentelemetry-cpp r=mvanstraten,jari

Differential Revision: https://phabricator.services.mozilla.com/D244098

third_party/opentelemetry-cpp/api/include/opentelemetry/context/context_value.h

@@ -10,11 +10,6 @@
 #include "opentelemetry/version.h"
 
 OPENTELEMETRY_BEGIN_NAMESPACE
-namespace baggage
-{
-class Baggage;
-}  // namespace baggage
-
 namespace trace
 {
 class Span;
@@ -29,7 +24,6 @@ using ContextValue = nostd::variant<nostd::monostate,
                                     uint64_t,
                                     double,
                                     nostd::shared_ptr<trace::Span>,
-                                    nostd::shared_ptr<trace::SpanContext>,
-                                    nostd::shared_ptr<baggage::Baggage>>;
+                                    nostd::shared_ptr<trace::SpanContext>>;
 }  // namespace context
 OPENTELEMETRY_END_NAMESPACE

third_party/opentelemetry-cpp/api/include/opentelemetry/std/variant.h

@@ -220,9 +220,13 @@ inline constexpr bool holds_alternative(const variant<Ts...> &v) noexcept
   return v.index() == I;
 }
 
-template <typename T, typename... Ts>
-inline constexpr bool holds_alternative(const variant<Ts...> &v) noexcept
+template <typename T, template<typename...> typename U, typename... Ts>
+inline constexpr bool holds_alternative(const U<Ts...> &v) noexcept
 {
+  // Clang 18.1.7 on Ubuntu 24.04 does not disambiguate between this
+  // and std::holds_alternative if argument type is std::variant<Ts...>
+  static_assert(std::is_same_v<U<Ts...>, std::variant<Ts...>>,
+                "Unsupported argument type");
   return std::holds_alternative<T, Ts...>(v);
 }