Fix 20778 - Ensure that _d_print_throwable prints the entire message

[MoonlightSentinel]

The previous implementation simply forwarded the pointer + length to
fprintf and didn't check the return value. This caused the message to
be truncated for the following cases:

• it contains \0 (the bug report)
• the length is greater than int.max

This commit changes the implementation s.t. it uses fwrite instead
which doesn't stop at \0 and (theoretically) supports lengths up to
size_t.max

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Also added a commit to make test/exceptions less noisy (because the huge_message test would generate a huge log entry)

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20778	regression	exception messages with nulls within are treated inconsistently

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + druntime#3787"

[kinke]

Could https://www.cplusplus.com/reference/cstdio/fwrite/ be a simpler option to just write the whole thing without stopping at nulls?

[MoonlightSentinel]

Could cplusplus.com/reference/cstdio/fwrite be a simpler option to just write the whole thing without stopping at nulls?

You're rigth, fwrite is a lot simpler. In theory it even supports larger messages (>= int.max) - but that behaviour doesn't seem to be portable (the test for huge messages failed on some machines, I've removed it because it's a highly unlikely case).