fix: network capture tests should fail if we exhaust the body

[pauldambra]

part of responding to https://github.com/PostHog/posthog/issues/24471 due to the unexpected consequences of https://github.com/PostHog/posthog-js/pull/1351

it is very hard to test for all unexpected consequences of changes to code 🙈

but we do at least now know for sure that that we cannot rely on request/response objects being readable and that we should not read them and then pass them on

Here's the test failing in CI and showing we would have avoided all of the painful impact for folk

  1 failing
  1) Session recording
       network capture - when fetch wrapper is not badly behaved
         it sends network payloads:
     TypeError: The following error originated from your test code, not from Cypress. It was caused by an unhandled promise rejection.
  > Failed to execute 'fetch' on 'Window': Cannot construct a Request with a Request object that has already been used.

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[pauldambra]

@daibhin @neilkakkar just a heads up on this in case you spot anything, but don't worry too much, it's very much a spike at the moment

[github-actions[bot]]

Size Change: +213 B (+0.02%)

Total Size: 1.17 MB

Filename	Size	Change
dist/array.full.js	335 kB	+71 B (+0.02%)
dist/recorder-v2.js	110 kB	+71 B (+0.06%)
dist/recorder.js	110 kB	+71 B (+0.06%)

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `dist/array.js` | 156 kB | | `dist/exception-autocapture.js` | 10.4 kB | | `dist/main.js` | 157 kB | | `dist/module.js` | 156 kB | | `dist/surveys-preview.js` | 59.8 kB | | `dist/surveys.js` | 66 kB | | `dist/tracing-headers.js` | 8.26 kB | | `dist/web-vitals.js` | 5.79 kB |

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