Failure due to recent PR for "storage class for several enum types"

[martenrichter]

The following commit
37de445
causes compiler errors such as:

[282/533] Building CXX object CMakeFiles/gquiche.dir/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc.o
FAILED: CMakeFiles/gquiche.dir/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc.o 
/usr/bin/c++ -DNAPI_VERSION=6 -D_ITERATOR_DEBUG_LEVEL=0 -D_LARGEFILE64_SOURCE=1 -I/workspaces/webtransport/transports/http3-quiche/platform -I/workspaces/webtransport/transports/http3-quiche/third_party/quiche -I/workspaces/webtransport/transports/http3-quiche/third_party/boringssl/src/include -I/workspaces/webtransport/transports/http3-quiche/third_party/abseil-cpp -I/workspaces/webtransport/transports/http3-quiche/third_party/googleurl -I/workspaces/webtransport/transports/http3-quiche/third_party/zlib -I/workspaces/webtransport/transports/http3-quiche/build_linux_x64/third_party/zlib -I/workspaces/webtransport/transports/http3-quiche/. -I/workspaces/webtransport/transports/http3-quiche/build_linux_x64 -I/workspaces/webtransport/node_modules/node-api-headers/include -I/workspaces/webtransport/node_modules/node-addon-api -I/workspaces/webtransport/transports/http3-quiche/third_party/protobuf/src -I/workspaces/webtransport/transports/http3-quiche/third_party/protobuf/third_party/utf8_range -DBUILDING_NODE_EXTENSION -g -std=gnu++20 -fPIC -MD -MT CMakeFiles/gquiche.dir/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc.o -MF CMakeFiles/gquiche.dir/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc.o.d -o CMakeFiles/gquiche.dir/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc.o -c /workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc
In file included from /workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.h:12,
                 from /workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/decoder/hpack_decoder_listener.cc:5:
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:22:6: warning: elaborated-type-specifier for a scoped enum must not use the 'class' keyword
   22 | enum class HpackEntryType : uint8_t {
      | ~~~~ ^~~~~
      |      -----
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:22:27: error: found ':' in nested-name-specifier, expected '::'
   22 | enum class HpackEntryType : uint8_t {
      |                           ^
      |                           ::
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:22:12: error: 'HpackEntryType' has not been declared
   22 | enum class HpackEntryType : uint8_t {
      |            ^~~~~~~~~~~~~~
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:22:37: error: expected unqualified-id before '{' token
   22 | enum class HpackEntryType : uint8_t {
      |                                     ^
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:55:50: error: 'HpackEntryType' was not declared in this scope; did you mean 'HpackEntryTypeToString'?
   55 | QUICHE_EXPORT std::string HpackEntryTypeToString(HpackEntryType v);
      |                                                  ^~~~~~~~~~~~~~
      |                                                  HpackEntryTypeToString
/workspaces/webtransport/transports/http3-quiche/third_party/quiche/quiche/http2/hpack/http2_hpack_constants.h:58:59: error: 'HpackEntryType' has not been declared
   58 | QUICHE_EXPORT std::ostream& operator<<(std::ostream& out, HpackEntryType v);
      |                                                           ^~~~~~~~~~~~~~

The reason is that uint8_t is not defined. Adding

#include <cstdint>

to http2_hpack_constants.h fixes the problem.
@birenroy can you please look into it and fix it?
Thanks!