Devtools usability fix: revisit decision to truncate network responses at 1MB

[mixu]

Looking at network responses is a frequently used feature for web development. 

However, Firefox makes it quite unergonomic to look at network responses because network responses are cut off at 1MB.

This might have been a reasonable default a decade ago, but with increasingly powerful developer machines and increasingly large response payloads it seems like an outdated default that should be bumped up to 10MB or even 100MB. As a user, I can adjust it by changing `devtools.netmonitor.responseBodyLimit` but that doesn't really "fix" the issue - I don't really want to have to do that on every single machine I use and every single time I start using Firefox on a new machine. It also adds friction to adopting Firefox: let's say I do convince folks to switch to Firefox; well, here is another annoying thing to tweak. 

[Jon]

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