patch 9.2.0307: more mismatches between return types and documentation

patch 9.2.0307: more mismatches between return types and documentation

Problem:  more mismatches between return types and documentation
Solution: Update documentation, fix return type for remote_foreground()
          and test_mswin_event() (Hirohito Higashi)

Doc summary table fixes:
- ch_info: String -> Dict
- spellbadword: String -> List
- undotree: List -> Dict
- test_getvalue: any -> Number
- instanceof, popup_filter_menu, popup_filter_yesno: Number -> Bool
- remote_foreground: Number -> none
- test_mswin_event: bool -> Bool

evalfunc.c fixes:
- remote_foreground: ret_string -> ret_void
- test_mswin_event: ret_number -> ret_bool

Detail "Return type:" fixes:
- instanceof: Number -> vim9-boolean
- remote_foreground: Number -> void
- popup_filter_menu, popup_filter_yesno: Number -> vim9-boolean

related: #19922
closes:  #19923

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>