encoding/csv: add a Fuzz function
encoding/csv: add a Fuzz function

Adds a sample Fuzz test function to package encoding/csv based on
https://github.com/dvyukov/go-fuzz-corpus/blob/master/csv/main.go

Updates #19109
Updates #31309

Change-Id: Ieb0cb6caa1df72dbb7e29df4bdeed0bfa91187d3
Reviewed-on: https://go-review.googlesource.com/c/go/+/174302
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,CAFxX/go,josharian/go,akutz/go,cloudflare/go,CAFxX/go,CAFxX/go,akutz/go,josharian/go,cloudflare/go,cloudflare/go,nawawi/go,CAFxX/go,CAFxX/go,josharian/go,akutz/go,nawawi/go,akutz/go,akutz/go,josharian/go,josharian/go,CAFxX/go,josharian/go,golang/go,nawawi/go,golang/go,akutz/go,akutz/go,golang/go,cloudflare/go,golang/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go,golang/go,cloudflare/go,josharian/go,nawawi/go,golang/go,golang/go,nawawi/go,akutz/go,josharian/go,nawawi/go