Add support for diagnostic tags from LSP 3.15

[krassowski]

References

Add support for diagnostic tags (DiagnosticTag) from LSP 3.15.

Code changes

Adds two new CSS classes:

• cm-lsp-diagnostic-tag-Unnecessary
• cm-lsp-diagnostic-tag-Deprecated

moves severity determination code so it is not run if we don't need to update the diagnostic.

User-facing changes

1. Strike-through is shown for deprecated items:
   
2. Unused code is faded out:
   TBD

Backwards-incompatible changes

None

Chores

• linted
• tested
• documented
• changelog entry

[github-actions]

👈 Launch a binder notebook on branch jupyter-lsp/jupyterlab-lsp/improve-diagnostics

[krassowski]

It looks like inclusion of pyls-memestra breaks LSP diagnostics on Windows.

[krassowski]

Yup, the lab.log shows:

Exception in thread Thread-4:
Traceback (most recent call last):
  File "C:\Miniconda3\envs\test\lib\threading.py", line 1009, in _bootstrap_inner
    self.run()
  File "C:\Miniconda3\envs\test\lib\threading.py", line 1371, in run
    self.function(*self.args, **self.kwargs)
  File "C:\Miniconda3\envs\test\lib\site-packages\pylsp\_utils.py", line 33, in run
    return func(*args, **kwargs)
  File "C:\Miniconda3\envs\test\lib\site-packages\pylsp\python_lsp.py", line 299, in lint
    flatten(self._hook('pylsp_lint', doc_uri, is_saved=is_saved))
  File "C:\Miniconda3\envs\test\lib\site-packages\pylsp\python_lsp.py", line 156, in _hook
    return hook_handlers(config=self.config, workspace=workspace, document=doc, **kwargs)
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_hooks.py", line 265, in __call__
    return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_manager.py", line 80, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_manager.py", line 327, in traced_hookexec
    return outcome.get_result()
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_result.py", line 60, in get_result
    raise ex[1].with_traceback(ex[2])
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_result.py", line 33, in from_call
    result = func()
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_manager.py", line 324, in <lambda>
    lambda: oldcall(hook_name, hook_impls, kwargs, firstresult)
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_callers.py", line 60, in _multicall
    return outcome.get_result()
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_result.py", line 60, in get_result
    raise ex[1].with_traceback(ex[2])
  File "C:\Miniconda3\envs\test\lib\site-packages\pluggy\_callers.py", line 39, in _multicall
    res = hook_impl.function(*args)
  File "C:\Miniconda3\envs\test\lib\site-packages\pyls_memestra\plugin.py", line 32, in pylsp_lint
    print("pyls_lint \U0001f414")
  File "C:\Miniconda3\envs\test\lib\encodings\cp1252.py", line 19, in encode
    return codecs.charmap_encode(input,self.errors,encoding_table)[0]
UnicodeEncodeError: 'charmap' codec can't encode character '\U0001f414' in position 10: character maps to <undefined>

Which is basically QuantStack/pyls-memestra#50