`report-multiple-violations-{01,02}` don't conform with the spec

[TimvdLippe]

Servo implemented response CSP checks and therefore fails tests/wpt/tests/content-security-policy/reporting/report-multiple-violations-01.html. This test ensures that 2 reports are sent. However, in case of report-only mode, then 4 reports are sent: 2 for both requests and 2 for both responses.

It seems like Safari also reports 4: https://wpt.fyi/results/content-security-policy/reporting/report-multiple-violations-01.html?label=experimental&label=master&aligned

Should we update the test to expect 4? Note that in the event that this is an enforce header (e.g. no report-only), then this would correctly send 2 reports, as the response check is never executed.

Similarly, https://wpt.fyi/results/content-security-policy/reporting/report-multiple-violations-02.html?label=experimental&label=master&aligned isn't specified anywhere with regards to deduplication. Only Chrome appears to implement this. Should we update the test to adhere to the other browsers (including Servo) or is Chrome's behavior preferable?