Change FLAGS_max_inbound_header_list_size type to int32_t.
Change FLAGS_max_inbound_header_list_size type to int32_t.

size_t flags cannot be supported on Chromium, because on some platforms it is a
type separate from other integral types, so GetQuicheFlagImpl() would need its
own overload, whereas on other platforms it is an alias of another integral
type, and the overloads would clash with "multiple definition" error.

PiperOrigin-RevId: 389186181

google/quiche,google/quiche,google/quiche,google/quiche