[dev.fuzz] internal/fuzz: don't use temporary buffers
[dev.fuzz] internal/fuzz: don't use temporary buffers

We're already allocating a huge amount of space at the end of each byte
slice, so just use that for scratch space instead of allocating a new
temporary buffer.

Change-Id: Ie075a199d4ac5dd5789949af2a19815c3025b809
Reviewed-on: https://go-review.googlesource.com/c/go/+/314272
Trust: Roland Shoemaker <0d270388f2f92757a5de0f4bd891d3b392c44c4f@golang.org>
Trust: Katie Hockman <e321a8fd89c4908465ddaf8d5d0d62480efacb63@golang.org>
Run-TryBot: Roland Shoemaker <0d270388f2f92757a5de0f4bd891d3b392c44c4f@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Katie Hockman <e321a8fd89c4908465ddaf8d5d0d62480efacb63@golang.org>

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