Support CSP report-only header (#36623)

This turned out to be a full rabbit hole. The new header
is parsed in the new `parse_csp_list_from_metadata` which
sets `disposition` to `report.

I was testing this with
`script-src-report-only-policy-works-with-external-hash-policy.html`
which was blocking the script incorrectly. Turns out that there
were multiple bugs in the CSP library, as well as a missing
check in `fetch` to report violations.

Additionally, in several locations we were manually reporting csp
violations, instead of the new `global.report_csp_violations`. As
a result of that, they would double report, since the report-only
header would be appended as a policy and now would report twice.

Now, all callsides use `global.report_csp_violations`. As a nice
side-effect, I added the code to set source file information,
since that was already present for the `eval` check, but nowhere
else.

Part of #36437

Requires servo/rust-content-security-policy#5

---------

Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
Signed-off-by: Tim van der Lippe <TimvdLippe@users.noreply.github.com>

components/script/timers.rs

@@ -421,8 +421,7 @@ impl JsTimers {
     ) -> i32 {
         let callback = match callback {
             TimerCallback::StringTimerCallback(code_str) => {
-                let cx = GlobalScope::get_cx();
-                if global.is_js_evaluation_allowed(cx) {
+                if global.is_js_evaluation_allowed(code_str.as_ref()) {
                     InternalTimerCallback::StringTimerCallback(code_str)
                 } else {
                     return 0;