Continuation of #5147 .. typification of the engine processors.

BTW:

- removed obsolete engine property https_support
- fixed & improved currency_convert
- engine instances can now implement a engine.setup method

[#5147] https://github.com/searxng/searxng/pull/5147

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

- pyright configuration [1]_
- stub files: types-lxml [2]_
- addition of various type hints
- enable use of new type system features on older Python versions [3]_
- ``.tool-versions`` - set python to lowest version we support (3.10.18) [4]_:
  Older versions typically lack some typing features found in newer Python
  versions.  Therefore, for local type checking (before commit), it is necessary
  to use the older Python interpreter.

.. [1] https://docs.basedpyright.com/v1.20.0/configuration/config-files/
.. [2] https://pypi.org/project/types-lxml/
.. [3] https://typing-extensions.readthedocs.io/en/latest/#
.. [4] https://mise.jdx.dev/configuration.html#tool-versions

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Format: reST

In the past, some files were tested with the standard profile, others with a
profile in which most of the messages were switched off ... some files were not
checked at all.

- ``PYLINT_SEARXNG_DISABLE_OPTION`` has been abolished
- the distinction ``# lint: pylint`` is no longer necessary
- the pylint tasks have been reduced from three to two

  1. ./searx/engines -> lint engines with additional builtins
  2. ./searx ./searxng_extra ./tests -> lint all other python files

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

Remove issue reported by Pylint 2.14.0:

- no-self-use: has been moved to optional extension [1]
- The refactoring checker now also raises 'consider-using-generator' messages
  for max(), min() and sum(). [2]

.pylintrc:
  - <option name>-hint has been removed since long, Pylint 2.14.0 raises an
    error on invalid options
  - bad-continuation and bad-whitespace have been removed [3]

[1] https://pylint.pycqa.org/en/latest/whatsnew/2/2.14/summary.html#removed-checkers
[2] https://pylint.pycqa.org/en/latest/whatsnew/2/2.14/full.html#what-s-new-in-pylint-2-14-0
[2] https://pylint.pycqa.org/en/latest/whatsnew/2/2.6/summary.html#summary-release-highlights

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

* allow not to record metrics (response time, etc...)
* this commit doesn't change the UI. If the metrics are disabled
  /stats and /stats/errors will return empty response.
  in /preferences, the columns response time and reliability will be empty.

This patch was generated by black [1]::

    make format.python

[1] https://github.com/psf/black

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

httpx.RequestError (subclass of httpx.HTTPError) has a property request.
This property raises a RuntimeError if the attributes _request is None.
To avoid a cascade of errors, this commit reads directly the _request attribute.