Support hunk-wise StageAndNext and UnstageAndNext (#25845)

This PR adds the `whole_excerpt` field to the actions:

- `git::StageAndNext`
- `git::UnstageAndNext`

Which is set by false by default, effectively, now staging and unstaging
with these actions is done hunk-by-hunk, this also affects the `Stage`
and
`Unstage` buttons in the Diff View toolbar.

A caveat: with this PR, there is no way to configure the buttons in the
Diff
View toolbar to restore the previous behavior, if we want, I think we
can make
it a setting, but let's see if anyone really wants that.

Release Notes:

- N/A

crates/git/src/git.rs

@@ -35,15 +35,23 @@ pub struct Push {
     pub options: Option<PushOptions>,
 }
 
-impl_actions!(git, [Push]);
+#[derive(Debug, Copy, Clone, PartialEq, Deserialize, JsonSchema)]
+pub struct StageAndNext {
+    pub whole_excerpt: bool,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Deserialize, JsonSchema)]
+pub struct UnstageAndNext {
+    pub whole_excerpt: bool,
+}
+
+impl_actions!(git, [Push, StageAndNext, UnstageAndNext]);
 
 actions!(
     git,
     [
         // per-hunk
         ToggleStaged,
-        StageAndNext,
-        UnstageAndNext,
         // per-file
         StageFile,
         UnstageFile,