CL 78735 description:

    time: add space padding layout strings(using underscore) for not only day but others

    As mentioned in #22802, only day component of layout string has space
    padding(represented by one underscore before its placeholder). This
    commit expands the rule for month, hour, minute and second.

    Updates #22802 (maybe fixes it)

Revert this CL because it breaks currently working formats that happen
to use underscores.

Fixes #23259

Change-Id: I64acaaca9b5b74785ee0f0be7910574e87daa649
Reviewed-on: https://go-review.googlesource.com/85998
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>