build: enable more EmmyLua checks

- call-non-callable
- missing-fields
- redefined-label
- redefined-local
- undefined-field
- unreachable-code

Promote redefined-local and unreachable-code to warnings.

Fix DOS line-ending handling for multiline semantic tokens, and support
intersection types in the help parser.

AI-assisted

runtime/lua/vim/re.lua

@@ -214,6 +214,7 @@ local exp = m.P{ "Exp",
             ((m.V"Definition" / firstdef) * (m.V"Definition" % adddef)^0) / mm.P
 }
 
+--- @type vim.lpeg.Pattern
 local pattern = S * m.Cg(m.Cc(false), "G") * exp / mm.P * (-any + patt_error)