Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/gpui/src/platform/windows/direct_write.rs

@@ -1,7 +1,7 @@
 use std::{borrow::Cow, sync::Arc};
 
 use ::util::ResultExt;
-use anyhow::{Result, anyhow};
+use anyhow::Result;
 use collections::HashMap;
 use itertools::Itertools;
 use parking_lot::{RwLock, RwLockUpgradableReadGuard};
@@ -729,7 +729,7 @@ impl DirectWriteState {
         glyph_bounds: Bounds<DevicePixels>,
     ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
         if glyph_bounds.size.width.0 == 0 || glyph_bounds.size.height.0 == 0 {
-            return Err(anyhow!("glyph bounds are empty"));
+            anyhow::bail!("glyph bounds are empty");
         }
 
         let font_info = &self.fonts[params.font_id.0];
@@ -1301,7 +1301,7 @@ fn get_postscript_name(font_face: &IDWriteFontFace3, locale: &str) -> Result<Str
         )?
     };
     if !exists.as_bool() || info.is_none() {
-        return Err(anyhow!("No postscript name found for font face"));
+        anyhow::bail!("No postscript name found for font face");
     }
 
     get_name(info.unwrap(), locale)
@@ -1393,9 +1393,7 @@ fn get_name(string: IDWriteLocalizedStrings, locale: &str) -> Result<String> {
                 &mut exists as _,
             )?
         };
-        if !exists.as_bool() {
-            return Err(anyhow!("No localised string for {}", locale));
-        }
+        anyhow::ensure!(exists.as_bool(), "No localised string for {locale}");
     }
 
     let name_length = unsafe { string.GetStringLength(locale_name_index) }? as usize;