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/install_cli/src/install_cli.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use client::ZED_URL_SCHEME;
 use gpui::{AppContext as _, AsyncApp, Context, PromptLevel, Window, actions};
 use release_channel::ReleaseChannel;
@@ -55,11 +55,8 @@ async fn install_script(cx: &AsyncApp) -> Result<PathBuf> {
         .output()
         .await?
         .status;
-    if status.success() {
-        Ok(link_path.into())
-    } else {
-        Err(anyhow!("error running osascript"))
-    }
+    anyhow::ensure!(status.success(), "error running osascript");
+    Ok(link_path.into())
 }
 
 pub async fn register_zed_scheme(cx: &AsyncApp) -> anyhow::Result<()> {