Add configurable options support for redpen linter (#5006)

Redpen linter previously had hardcoded command-line options and duplicated
linter definitions across all supported file types (asciidoc, markdown,
review, rst, tex, text). This refactoring centralizes the linter definition
and adds support for user-configurable options via g:ale_redpen_options.

Key changes:
- Created ale#handlers#redpen#DefineLinter() to eliminate code duplication
- Added ale#handlers#redpen#GetCommand() to support configurable options
- All file types now use shared configuration and command building
- Added comprehensive test coverage for option handling
- Updated documentation for all affected file types

This allows users to customize redpen behavior with additional command-line
options while maintaining backward compatibility and reducing maintenance
overhead.

doc/ale-text.txt

@@ -51,5 +51,11 @@ write-good                                                *ale-text-write-good*
 See |ale-write-good-options|
 
 
+===============================================================================
+redpen                                                        *ale-text-redpen*
+
+See |ale-redpen-options|
+
+
 ===============================================================================
   vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl: