text/template: implement short-circuit and, or

text/template: implement short-circuit and, or

Making the builtin and and or functions use short-circuit
evaluation was accepted as a proposal in April 2019,
but we never got around to implementing it. Do that.

Fixes #31103.

Change-Id: Ia43d4a9a6b0ab814f2dd3471ebaca3e7bb1505cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/321490
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>