Rename custom-typeshed-dir, target-version and current-directory CLI options (#14930)

## Summary

This PR renames the `--custom-typeshed-dir`, `target-version`, and
`--current-directory` cli options to `--typeshed`,
`--python-version`, and `--project` as discussed in the CLI proposal
document.
I added aliases for `--target-version` (for Ruff compat) and
`--custom-typeshed-dir` (for Alex)

## Test Plan

Long help

```
An extremely fast Python type checker.

Usage: red_knot [OPTIONS] [COMMAND]

Commands:
  server  Start the language server
  help    Print this message or the help of the given subcommand(s)

Options:
      --project <PROJECT>
          Run the command within the given project directory.
          
          All `pyproject.toml` files will be discovered by walking up the directory tree from the project root, as will the project's virtual environment (`.venv`).
          
          Other command-line arguments (such as relative paths) will be resolved relative to the current working directory."#,

      --venv-path <PATH>
          Path to the virtual environment the project uses.
          
          If provided, red-knot will use the `site-packages` directory of this virtual environment to resolve type information for the project's third-party dependencies.

      --typeshed-path <PATH>
          Custom directory to use for stdlib typeshed stubs

      --extra-search-path <PATH>
          Additional path to use as a module-resolution source (can be passed multiple times)

      --python-version <VERSION>
          Python version to assume when resolving types
          
          [possible values: 3.7, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13]

  -v, --verbose...
          Use verbose output (or `-vv` and `-vvv` for more verbose output)

  -W, --watch
          Run in watch mode by re-running whenever files change

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version
```

Short help 

```
An extremely fast Python type checker.

Usage: red_knot [OPTIONS] [COMMAND]

Commands:
  server  Start the language server
  help    Print this message or the help of the given subcommand(s)

Options:
      --project <PROJECT>         Run the command within the given project directory
      --venv-path <PATH>          Path to the virtual environment the project uses
      --typeshed-path <PATH>      Custom directory to use for stdlib typeshed stubs
      --extra-search-path <PATH>  Additional path to use as a module-resolution source (can be passed multiple times)
      --python-version <VERSION>  Python version to assume when resolving types [possible values: 3.7, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13]
  -v, --verbose...                Use verbose output (or `-vv` and `-vvv` for more verbose output)
  -W, --watch                     Run in watch mode by re-running whenever files change
  -h, --help                      Print help (see more with '--help')
  -V, --version                   Print version

```

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/red_knot/src/python_version.rs

@@ -0,0 +1,68 @@
+/// Enumeration of all supported Python versions
+///
+/// TODO: unify with the `PythonVersion` enum in the linter/formatter crates?
+#[derive(Copy, Clone, Hash, Debug, PartialEq, Eq, PartialOrd, Ord, Default, clap::ValueEnum)]
+pub enum PythonVersion {
+    #[value(name = "3.7")]
+    Py37,
+    #[value(name = "3.8")]
+    Py38,
+    #[default]
+    #[value(name = "3.9")]
+    Py39,
+    #[value(name = "3.10")]
+    Py310,
+    #[value(name = "3.11")]
+    Py311,
+    #[value(name = "3.12")]
+    Py312,
+    #[value(name = "3.13")]
+    Py313,
+}
+
+impl PythonVersion {
+    const fn as_str(self) -> &'static str {
+        match self {
+            Self::Py37 => "3.7",
+            Self::Py38 => "3.8",
+            Self::Py39 => "3.9",
+            Self::Py310 => "3.10",
+            Self::Py311 => "3.11",
+            Self::Py312 => "3.12",
+            Self::Py313 => "3.13",
+        }
+    }
+}
+
+impl std::fmt::Display for PythonVersion {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+impl From<PythonVersion> for red_knot_python_semantic::PythonVersion {
+    fn from(value: PythonVersion) -> Self {
+        match value {
+            PythonVersion::Py37 => Self::PY37,
+            PythonVersion::Py38 => Self::PY38,
+            PythonVersion::Py39 => Self::PY39,
+            PythonVersion::Py310 => Self::PY310,
+            PythonVersion::Py311 => Self::PY311,
+            PythonVersion::Py312 => Self::PY312,
+            PythonVersion::Py313 => Self::PY313,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::python_version::PythonVersion;
+
+    #[test]
+    fn same_default_as_python_version() {
+        assert_eq!(
+            red_knot_python_semantic::PythonVersion::from(PythonVersion::default()),
+            red_knot_python_semantic::PythonVersion::default()
+        );
+    }
+}