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>

Cargo.toml

@@ -243,3 +243,7 @@ codegen-units = 1
 #
 # [patch."https://github.com/servo/<repository>"]
 # <crate> = { path = "/path/to/local/checkout" }
+#
+# [patch."https://github.com/servo/rust-content-security-policy"]
+# content-security-policy = { path = "../rust-content-security-policy/" }
+# content-security-policy = { git = "https://github.com/timvdlippe/rust-content-security-policy/", branch = "fix-report-checks", features = ["serde"] }