It wasn't obeyed in the case where the MarshalJSON method uses a pointer
receiver, and the encoder grabs the address of a value to find that
method. addrMarshalerEncoder is the function that does this work, but it
ignored opts.escapeHTML.

Here's the before and after of the added test case, which was failing
before the fix. Now the two cases are correct and consistent.

	{"NonPtr":"<str>","Ptr":"\u003cstr\u003e"}
	{"NonPtr":"<str>","Ptr":"<str>"}

Fixes #32896.

Change-Id: Idc53077ece074973558bd3bb5ad036380db0d02c
Reviewed-on: https://go-review.googlesource.com/c/go/+/184757
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Caleb Spare <cespare@gmail.com>