Update CLI to respect fix applicability (#7769)

Rebase of https://github.com/astral-sh/ruff/pull/5119 authored by
@evanrittenhouse with additional refinements.

## Changes

- Adds `--unsafe-fixes` / `--no-unsafe-fixes` flags to `ruff check`
- Violations with unsafe fixes are not shown as fixable unless opted-in
- Fix applicability is respected now
    - `Applicability::Never` fixes are no longer applied
    - `Applicability::Sometimes` fixes require opt-in
    - `Applicability::Always` fixes are unchanged
- Hints for availability of `--unsafe-fixes` added to `ruff check`
output

## Examples

Check hints at hidden unsafe fixes
```
❯ ruff check example.py --no-cache --select F601,W292
example.py:1:14: F601 Dictionary key literal `'a'` repeated
example.py:2:15: W292 [*] No newline at end of file
Found 2 errors.
[*] 1 fixable with the `--fix` option (1 hidden fix can be enabled with the `--unsafe-fixes` option).
```

We could add an indicator for which violations have hidden fixes in the
future.

Check treats unsafe fixes as applicable with opt-in
```
❯ ruff check example.py --no-cache --select F601,W292 --unsafe-fixes
example.py:1:14: F601 [*] Dictionary key literal `'a'` repeated
example.py:2:15: W292 [*] No newline at end of file
Found 2 errors.
[*] 2 fixable with the --fix option.
```

Also can be enabled in the config file

```
❯ cat ruff.toml
unsafe-fixes = true
```

And opted-out per invocation

```
❯ ruff check example.py --no-cache --select F601,W292 --no-unsafe-fixes
example.py:1:14: F601 Dictionary key literal `'a'` repeated
example.py:2:15: W292 [*] No newline at end of file
Found 2 errors.
[*] 1 fixable with the `--fix` option (1 hidden fix can be enabled with the `--unsafe-fixes` option).
```

Diff does not include unsafe fixes
```
❯ ruff check example.py --no-cache --select F601,W292 --diff
--- example.py
+++ example.py
@@ -1,2 +1,2 @@
 x = {'a': 1, 'a': 1}
-print(('foo'))
+print(('foo'))
\ No newline at end of file

Would fix 1 error.
```

Unless there is opt-in
```
❯ ruff check example.py --no-cache --select F601,W292 --diff --unsafe-fixes
--- example.py
+++ example.py
@@ -1,2 +1,2 @@
-x = {'a': 1}
-print(('foo'))
+x = {'a': 1, 'a': 1}
+print(('foo'))
\ No newline at end of file

Would fix 2 errors.
```

https://github.com/astral-sh/ruff/pull/7790 will improve the diff
messages following this pull request

Similarly, `--fix` and `--fix-only` require the `--unsafe-fixes` flag to
apply unsafe fixes.

## Related

Replaces #5119
Closes https://github.com/astral-sh/ruff/issues/4185
Closes https://github.com/astral-sh/ruff/issues/7214
Closes https://github.com/astral-sh/ruff/issues/4845
Closes https://github.com/astral-sh/ruff/issues/3863
Addresses https://github.com/astral-sh/ruff/issues/6835
Addresses https://github.com/astral-sh/ruff/issues/7019
Needs follow-up https://github.com/astral-sh/ruff/issues/6962
Needs follow-up https://github.com/astral-sh/ruff/issues/4845
Needs follow-up https://github.com/astral-sh/ruff/issues/7436
Needs follow-up https://github.com/astral-sh/ruff/issues/7025
Needs follow-up https://github.com/astral-sh/ruff/issues/6434
Follow-up #7790 
Follow-up https://github.com/astral-sh/ruff/pull/7792

---------

Co-authored-by: Evan Rittenhouse <evanrittenhouse@gmail.com>

crates/ruff_diagnostics/src/fix.rs

@@ -6,21 +6,21 @@ use ruff_text_size::{Ranged, TextSize};
 use crate::edit::Edit;
 
 /// Indicates if a fix can be applied.
-#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "serde", serde(rename_all = "lowercase"))]
 pub enum Applicability {
-    /// The fix is safe and can always be applied.
-    /// The fix is definitely what the user intended, or it maintains the exact meaning of the code.
-    Always,
+    /// The fix is unsafe and should only be manually applied by the user.
+    /// The fix is likely to be incorrect or the resulting code may have invalid syntax.
+    Never,
 
     /// The fix is unsafe and should only be applied with user opt-in.
     /// The fix may be what the user intended, but it is uncertain; the resulting code will have valid syntax.
     Sometimes,
 
-    /// The fix is unsafe and should only be manually applied by the user.
-    /// The fix is likely to be incorrect or the resulting code may have invalid syntax.
-    Never,
+    /// The fix is safe and can always be applied.
+    /// The fix is definitely what the user intended, or it maintains the exact meaning of the code.
+    Always,
 }
 
 /// Indicates the level of isolation required to apply a fix.
@@ -133,4 +133,9 @@ impl Fix {
         self.isolation_level = isolation;
         self
     }
+
+    /// Return [`true`] if this [`Fix`] should be applied with at a given [`Applicability`].
+    pub fn applies(&self, applicability: Applicability) -> bool {
+        self.applicability >= applicability
+    }
 }