tombi: support its LSP (#5022)

* tombi: support its LSP
* tombi: support linting and formatting

test/fixers/test_tombi_format_fixer_callback.vader

@@ -0,0 +1,33 @@
+Before:
+  Save g:ale_toml_tombi_executable
+  Save g:ale_toml_tombi_format_options
+
+  " Use an invalid global executable, so we don't match it.
+  let g:ale_toml_tombi_executable = 'xxxinvalid'
+  let g:ale_toml_tombi_format_options = ''
+
+  call ale#test#SetDirectory('/testplugin/test/fixers')
+
+After:
+  Restore
+
+  call ale#test#RestoreDirectory()
+
+Execute(The tombi format callback should return the correct default values):
+
+  AssertEqual
+  \ {
+  \   'command': ale#Escape('xxxinvalid') . ' format',
+  \ },
+  \ ale#fixers#tombi_format#Fix(bufnr(''))
+
+Execute(The tombi format callback should include custom options):
+  let g:ale_toml_tombi_format_options = "--offline"
+
+  AssertEqual
+  \ {
+  \   'command': ale#Escape('xxxinvalid')
+  \     . ' format'
+  \     . ' ' . g:ale_toml_tombi_format_options
+  \ },
+  \ ale#fixers#tombi_format#Fix(bufnr(''))