Add line_ending setting to control line-ending normalization (#54356)

Closes #49581

Adds a `line_ending` language setting that controls how line endings are
handled for new files and during format/save:

- `detect` (default) — detects existing line endings; new files use the
platform default
- `prefer_lf` / `prefer_crlf` — sets LF or CRLF for new files and files
with no existing convention, while preserving existing files
- `enforce_lf` / `enforce_crlf` — normalizes all line endings to LF or
CRLF on every format/save

The setting can be configured globally, per-language, or via
`.editorconfig`'s `end_of_line` property (which maps to `enforce_lf` /
`enforce_crlf`).

Release Notes:

- Added `line_ending` setting to control how line endings are handled
for new files and normalized on save.
- Added support for `.editorconfig` `end_of_line` property to enforce
line endings.

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>

docs/src/reference/all-settings.md

@@ -1618,6 +1618,56 @@ This setting enables integration with macOS’s native window tabbing feature. W
 
 `boolean` values
 
+## Line Ending
+
+- Description: How line endings should be handled for new files and during format and save. This can be specified on a per-language basis.
+- Setting: `line_ending`
+- Default: `detect`
+
+**Options**
+
+1. To detect existing line endings and otherwise use the platform default (`lf` on Unix, `crlf` on Windows), set it to `detect`:
+
+```json [settings]
+{
+  "line_ending": "detect"
+}
+```
+
+2. To prefer LF (`\n`) for new files and files with no existing line ending, use `prefer_lf`:
+
+```json [settings]
+{
+  "line_ending": "prefer_lf"
+}
+```
+
+3. To prefer CRLF (`\r\n`) for new files and files with no existing line ending, use `prefer_crlf`:
+
+```json [settings]
+{
+  "line_ending": "prefer_crlf"
+}
+```
+
+4. To enforce LF (`\n`) during format and save, use `enforce_lf`:
+
+```json [settings]
+{
+  "line_ending": "enforce_lf"
+}
+```
+
+5. To enforce CRLF (`\r\n`) during format and save, use `enforce_crlf`:
+
+```json [settings]
+{
+  "line_ending": "enforce_crlf"
+}
+```
+
+The [`.editorconfig`](https://editorconfig.org) `end_of_line` property overrides this setting and behaves like `enforce_lf` or `enforce_crlf`.
+
 ## Expand Excerpt Lines
 
 - Description: The default number of lines to expand excerpts in the multibuffer by
@@ -2772,6 +2822,7 @@ The following settings can be overridden for each specific language:
 
 - [`enable_language_server`](#enable-language-server)
 - [`ensure_final_newline_on_save`](#ensure-final-newline-on-save)
+- [`line_ending`](#line-ending)
 - [`format_on_save`](#format-on-save)
 - [`formatter`](#formatter)
 - [`hard_tabs`](#hard-tabs)