QUIC: fixed bulding perl module by reducing header pollution.

The ngx_http_perl_module module doesn't have a notion of including additional
search paths through --with-cc-opt, which results in compile error incomplete
type 'enum ssl_encryption_level_t' when building nginx without QUIC support.
The enum is visible from quic event headers and eventually pollutes ngx_core.h.

The fix is to limit including headers to compile units that are real consumers.

src/core/ngx_core.h

@@ -86,8 +86,6 @@ typedef void (*ngx_connection_handler_pt)(ngx_connection_t *c);
 #include <ngx_event_openssl.h>
 #if (NGX_OPENSSL_QUIC)
 #include <ngx_event_quic.h>
-#include <ngx_event_quic_transport.h>
-#include <ngx_event_quic_protection.h>
 #endif
 #endif
 #include <ngx_process_cycle.h>

src/event/ngx_event_quic.c

@@ -7,6 +7,8 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_event.h>
+#include <ngx_event_quic_transport.h>
+#include <ngx_event_quic_protection.h>
 
 
 /*  0-RTT and 1-RTT data exist in the same packet number space,

src/event/ngx_event_quic_protection.c

@@ -7,6 +7,8 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_event.h>
+#include <ngx_event_quic_transport.h>
+#include <ngx_event_quic_protection.h>
 
 
 #define NGX_QUIC_IV_LEN               12

src/event/ngx_event_quic_transport.c

@@ -7,6 +7,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_event.h>
+#include <ngx_event_quic_transport.h>
 
 
 #if (NGX_HAVE_NONALIGNED)