Fix markdownlint fixer and add markdownlint-cli2 (#5165)

* fix(tests): fix ale_c_build_dir_names being unset in tests (#5109)

- Use ale#Set() to set the ale_c_build_dir_names variable.
- Ensure SetUpLinterTest() is called before any Save commands in tests.
- Add c.vim to runtime before non-linter tests are executed.
- Remove workarounds in c.vim.

* feat: Load Prettier from cjs also

* fix: wrong command for markdownlint

* feat: explicit support for markdownlint-cli2

- Add markdownlint-cli2 linter and fixer, separate from markdownilnt-cli
- Rename markdownlint to markdownlint-cli
- Keep markdownlint as alias for markdownlint-cli

---------

Co-authored-by: w0rp <devw0rp@gmail.com>
Co-authored-by: Horacio Sanson <horacio.sanson@dena.jp>

ale_linters/markdown/markdownlint_cli2.vim

@@ -0,0 +1,29 @@
+" Author: Horacio Sanson
+" Description: Adds support for markdownlint-cli2
+
+call ale#Set('markdown_markdownlint_cli2_executable', 'markdownlint-cli2')
+call ale#Set('markdown_markdownlint_cli2_options', '')
+
+function! ale_linters#markdown#markdownlint_cli2#GetExecutable(buffer) abort
+    return ale#handlers#markdownlint#GetExecutable(
+    \   a:buffer,
+    \   'markdownlint_cli2',
+    \)
+endfunction
+
+function! ale_linters#markdown#markdownlint_cli2#GetCommand(buffer) abort
+    return ale#handlers#markdownlint#GetCommand(
+    \   a:buffer,
+    \   'markdownlint_cli2',
+    \)
+endfunction
+
+call ale#linter#Define('markdown', {
+\   'name': 'markdownlint_cli2',
+\   'aliases': ['markdownlint-cli2'],
+\   'executable': function('ale_linters#markdown#markdownlint_cli2#GetExecutable'),
+\   'lint_file': 1,
+\   'output_stream': 'both',
+\   'command': function('ale_linters#markdown#markdownlint_cli2#GetCommand'),
+\   'callback': 'ale#handlers#markdownlint#Handle',
+\})