Hsts: match header names case insensitively (CVE-2023-32762)

Header field names are always considered to be case-insensitive.

Pick-to: 6.5 6.5.1 6.2 5.15
Fixes: QTBUG-113392
Change-Id: Ifb4def4bb7f2ac070416cdc76581a769f1e52b43
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 1b736a8)

* asturmlechner 2023-05-23: Upstream backport to 5.15 taken from
  https://www.qt.io/blog/security-advisory-qt-network

src/network/access/qhsts.cpp

@@ -364,8 +364,8 @@ quoted-pair    = "\" CHAR
 bool QHstsHeaderParser::parse(const QList<QPair<QByteArray, QByteArray>> &headers)
 {
     for (const auto &h : headers) {
-        // We use '==' since header name was already 'trimmed' for us:
-        if (h.first == "Strict-Transport-Security") {
+        // We compare directly because header name was already 'trimmed' for us:
+        if (h.first.compare("Strict-Transport-Security", Qt::CaseInsensitive) == 0) {
             header = h.second;
             // RFC6797, 8.1:
             //