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/dap/src/proto_conversions.rs

@@ -1,4 +1,4 @@
-use anyhow::{Result, anyhow};
+use anyhow::{Context as _, Result};
 use client::proto::{
     self, DapChecksum, DapChecksumAlgorithm, DapEvaluateContext, DapModule, DapScope,
     DapScopePresentationHint, DapSource, DapSourcePresentationHint, DapStackFrame, DapVariable,
@@ -311,9 +311,9 @@ impl ProtoConversion for dap_types::Module {
     fn from_proto(payload: Self::ProtoType) -> Result<Self> {
         let id = match payload
             .id
-            .ok_or(anyhow!("All DapModule proto messages must have an id"))?
+            .context("All DapModule proto messages must have an id")?
             .id
-            .ok_or(anyhow!("All DapModuleID proto messages must have an id"))?
+            .context("All DapModuleID proto messages must have an id")?
         {
             proto::dap_module_id::Id::String(string) => dap_types::ModuleId::String(string),
             proto::dap_module_id::Id::Number(num) => dap_types::ModuleId::Number(num),