Fixes #740.

This reverts commits ea7c165b59 and
3d81c83132.

When "have 6 expectations and 4 region_highlight entries", the pure-zsh
implementation printed them as follows:

    not ok 7 - cardinality check - have 6 expectations and 4 region_highlight entries: «expected_region_highlight=( $'1 1 builtin' $'3 6 comment' $'8 13 comment' $'15 15 default' $'16 21 comment' $'22 22 default' )»
    «region_highlight=( $'0 1 builtin' $'2 6 comment' $'7 13 comment' $'14 22 default' )»
    # expected_region_highlight  '22 22 default'
    # '1 1 builtin'              region_highlight
    # '3 6 comment'              '0 1 builtin'
    # '8 13 comment'             '2 6 comment'
    # '15 15 default'            '7 13 comment'
    # '16 21 comment'            '14 22 default'

Whereas the column(1)-based implementation prints them as follows:

    not ok 7 - cardinality check - have 6 expectations and 4 region_highlight entries: «expected_region_highlight=( $'1 1 builtin' $'3 6 comment' $'8 13 comment' $'15 15 default' $'16 21 comment' $'22 22 default' )» «region_highlight=( $'0 1 builtin' $'2 6 comment' $'7 13 comment' $'14 22 default' )»
    # expected_region_highlight  region_highlight
    # '1 1 builtin'              '0 1 builtin'
    # '3 6 comment'              '2 6 comment'
    # '8 13 comment'             '7 13 comment'
    # '15 15 default'            '14 22 default'
    # '16 21 comment'
    # '22 22 default'

Ultimately, this difference is down to the pure-zsh implementation
getting the arguments as a single list, whereas paste(1) gets two
separate lists.

See the last commit,
bdb4e8b70e test harness: When the cardinality check fails, pretty-print \$expected_region_highlight and \$region_highlight.