Refs Devolutions#1257.

Implements Change 3 from the proposal in Devolutions#1257. Adds workspace-shared
`bail!` and `ensure!` macros to ironrdp-error so call-site verbosity for
typed errors matches anyhow::bail!/anyhow::ensure!.

### What changes

- `bail!(kind)` — empty context.
- `bail!(context, kind)` — explicit `&'static str` context.
- `bail!(context, kind, source: source)` — explicit context plus a chained
  source error.
- `ensure!(condition, kind)` — empty context.
- `ensure!(condition, context, kind)` — explicit context.

Both macros are `#[macro_export]`ed at the ironrdp-error crate root and use
`$crate::Error::new(...)` for hygiene. The kind type is inferred from the
enclosing function's return type (which must be `Result<_, Error<Kind>>` or
any alias resolving to it).

### Composition with #[track_caller]

Once Change 2 (Devolutions#1262) lands and `Error::new` is annotated `#[track_caller]`,
these macros automatically capture the location at the macro use site
(because the `Error::new` call expanded inside the macro is the caller of
its own constructor, and `#[track_caller]` resolves to the macro's caller).
This is the intended composition: Change 2 supplies the location, Change 3
supplies the call-site ergonomics, both compose without coordination.

### No deprecation of per-crate macros

The existing per-crate constructor macros (`decode_err!`, `encode_err!`,
`pdu_other_err!`, etc.) serve a different ergonomic pattern: they construct
an error to be passed to `?` or `.map_err(...)`, rather than performing an
early return. The shared `bail!`/`ensure!` are additive — they cover the
early-return patterns that previously required hand-written
`return Err(Error::new(...))` boilerplate. The per-crate constructor
macros remain useful for `.map_err(decode_err!(...))` style and are not
deprecated by this change.

### Public API impact

Strictly additive. Two new exported macros at the ironrdp-error crate root.
No changes to existing types, traits, or methods.

### no_std verification

All three feature combinations of ironrdp-error build cleanly:
- `cargo check -p ironrdp-error --no-default-features`
- `cargo check -p ironrdp-error --no-default-features --features alloc`
- `cargo check -p ironrdp-error --features std`

The macros use only fully-pathed std-free constructs (`::core::result::Result::Err`,
`$crate::Error::new`), so they work identically across feature combinations.

### xtask verification

- `cargo xtask check fmt`: clean
- `cargo xtask check lints`: clean
- `cargo xtask check locks`: clean
- `cargo xtask check typos`: clean
- `cargo xtask check tests`: clean

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