Fuzzer: Ignore V8 errors on uninitialized non-defaultable locals

[kripken]

See #5665 #5599, this is an existing issue and we have a workaround for it
using --dce, but it does not always work. I seem to be seeing this in higher
frequency since landing recent fuzzer improvements, so ignore it.

There is some risk of us missing real bugs here (that we validate and V8
does not), but this is a validation error which is not as serious as a difference
in behavior. And this is a long-standing issue that hasn't bitten us yet.

[tlively]

Would it be worth printing a warning or something for these ignored issues, just to keep them top of mind and maybe motivate us to fix them at some point?

[kripken]

Maybe we should do more for that, yeah. The amount ignored is reported, e.g.

ITERATION: 12884 seed: 14203204938912432813 size: 8923
(mean: 40738.996352064576, stddev: 26835.6222677628)
speed: 2.0233051433240834 iters/sec,  68669.57184038128
wasm_bytes/sec,  387 ignored                                                                                                                                                                                            

So we ignored 387 out of 12,884 there. But we could also report a breakdown of the reason for each ignored issue perhaps.