We have created a standardized `.editorconfig` file that can be used in any Arduino Tooling project:
https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/general/.editorconfig

The preferred approach is for the tasks to install their specific dependencies as needed, in a manner that does not
pollute the task user's environment. However, it doesn't appear to be feasible to do this with the shfmt and ShellCheck
tools used by the `shell:format` task, so the task user is responsible for installing this tool.

In the event the task user does not have such a tool installed (or installation not in PATH), the task should provide a
helpful error message, which is provided by this change.

This is the standardized shell script formatting style to be used in all Arduino Tooling projects, as defined in
`/.editorconfig`.

- Use standardized task name
- Add support for arbitrary file extensions and path configurations (which is not possible with the previous globstar
  approach)

GitHub Actions provides a paths filter feature that allows you to restrict workflow run triggers to changes to specific
paths within the repository. This can greatly improve the efficiency of the CI system by avoiding running irrelevant
checks. The effective use of this feature requires that the purpose of a workflow be focused on a specific type of file
or project component. Since collecting related jobs into a single workflow can be the best approach both from a
maintainer and contributor viewpoint, it makes sense to do this grouping based on component type rather than on category
of operation, as was previously done by the "Check formatting" workflow.

The "Check Shell" workflow is collects the linting and formatting checks specific to the project's Shell script files.

Since Windows doesn't have the concept of an executable file mode, and shell scripts not considered executable by Linux,
etc. will work fine if a shell is installed (e.g., Git Bash), shell scripts written or worked on by Windows developers
may not be executable. For this reason, it is especially helpful for the CI to do a check on the file mode of the
project's shell scripts, failing if they are not executable.

The `shell:check-formatting` task has no value to the developer, since they will be better off to just run the formatting
task. The CI also doesn't make use of this task, instead taking the superior approach of running the formatting task and
then checking for a diff. Since there is no use for this task, it should be removed.