Fix #4388: Fix pylsp and Pyright cwd

Add functions to compute the cwd to be the same as the project root for
pylsp and Pyright to work around issues in each language server when
they encounter modules that share the same name as first or third party
libraries.

test/linter/test_pyright.vader

@@ -10,6 +10,8 @@ After:
   call ale#assert#TearDownLinterTest()
 
 Execute(The command callback should return the correct default string):
+  call ale#test#SetFilename('./foo.py')
+
   AssertLinter
   \ 'pyright-langserver',
   \ ale#Escape('pyright-langserver') . ' --stdio'
@@ -30,6 +32,12 @@ Execute(The default configuration should be mostly empty):
 
   AssertLSPConfig {'python': {}}
 
+Execute(The cwd and project root should be detected correctly):
+  call ale#test#SetFilename('../test-files/python/with_virtualenv/subdir/foo/bar.py')
+
+  AssertLinterCwd ale#test#GetFilename('../test-files/python/with_virtualenv/subdir')
+  AssertLSPProject ale#test#GetFilename('../test-files/python/with_virtualenv/subdir')
+
 Execute(virtualenv paths should be set in configuration by default):
   call ale#test#SetFilename('../test-files/python/with_virtualenv/subdir/foo/bar.py')