Update default vim substitute command behavior and add support for 'g' flag (#28138)

This Pull Request updates the default behavior of the substitute (`s`)
command in vim mode to only replace the next match by default, instead
of all, and replace all matches only when the `g` flag is provided,
making it more similar to NeoVim's behavior.

In order to achieve this, the following changes were introduced:

- Update `BufferSearchBar::replace_next` to be a public method, so it
can be called from `Vim::replace_command` .
- Update the `Replacement::parse` to set the `should_replace_all` field
to `false` by default, and only set it to `true` if the `'g'` flag is
present in the query.
- Add support for when the `Replacement.should_replace_all` is set to
`false` in `Vim::replace_command`, so as to have it only replace the
next occurrence instead of all occurrences in the line.
- Introduce `BufferSearchBar::select_first_match` so as to activate the
first match on the line under the cursor.

Closes #24450 

Release Notes:

- Improved vim's substitute command so as to only replace the first
match by default, and replace all matches if the `'g'` flag is provided

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/project/src/search.rs

@@ -71,6 +71,7 @@ pub enum SearchQuery {
         whole_word: bool,
         case_sensitive: bool,
         include_ignored: bool,
+        one_match_per_line: bool,
         inner: SearchInputs,
     },
 }
@@ -116,6 +117,7 @@ impl SearchQuery {
         whole_word: bool,
         case_sensitive: bool,
         include_ignored: bool,
+        one_match_per_line: bool,
         files_to_include: PathMatcher,
         files_to_exclude: PathMatcher,
         buffers: Option<Vec<Entity<Buffer>>>,
@@ -156,6 +158,7 @@ impl SearchQuery {
             case_sensitive,
             include_ignored,
             inner,
+            one_match_per_line,
         })
     }
 
@@ -166,6 +169,7 @@ impl SearchQuery {
                 message.whole_word,
                 message.case_sensitive,
                 message.include_ignored,
+                false,
                 deserialize_path_matches(&message.files_to_include)?,
                 deserialize_path_matches(&message.files_to_exclude)?,
                 None, // search opened only don't need search remote
@@ -459,6 +463,19 @@ impl SearchQuery {
             Self::Regex { inner, .. } | Self::Text { inner, .. } => inner,
         }
     }
+
+    /// Whether this search should replace only one match per line, instead of
+    /// all matches.
+    /// Returns `None` for text searches, as only regex searches support this
+    /// option.
+    pub fn one_match_per_line(&self) -> Option<bool> {
+        match self {
+            Self::Regex {
+                one_match_per_line, ..
+            } => Some(*one_match_per_line),
+            Self::Text { .. } => None,
+        }
+    }
 }
 
 pub fn deserialize_path_matches(glob_set: &str) -> anyhow::Result<PathMatcher> {