runtime(sh): Add handling for ksh93 shared-state comsubs and mksh valsubs (vim/vim#13884)
This commit adds support for ksh93 shared-state command
substitutions (syntax: ${ command; }) and mksh's value
substitutions (syntax: ${|command;}) in the sh syntax script.
Also add a syntax test for ksh subshares with dumps included
to make sure it doesn't regress.
fixes: vim/vim#9514add31baeda
Co-authored-by: Johnothan King <johnothanking@protonmail.com>
46aa1936e4
