Revert "encoding/json: reduce unmarshal mallocs for unmapped fields"
Revert "encoding/json: reduce unmarshal mallocs for unmapped fields"

This reverts commit df68afd07ce67727 (https://golang.org/cl/33276)

Reason for revert: made other benchmarks worse

Fixes #20693 (details)
Updates #17914
Updates #10335

Change-Id: If451b620803ccb0536b89c76c4353d2185d57d7e
Reviewed-on: https://go-review.googlesource.com/47211
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

coreos/go-json