feat(error): record byte offset on decode and encode error variants

Reshapes the position-aware error approach per #1266 review feedback. Moves
position metadata out of the foundational `ironrdp-error` crate and onto the
decode and encode `*ErrorKind` enum variants where it actually applies.

Previously this PR added an optional `ErrorPosition { offset, field }` slot
to `Error<Kind>`'s `ErrorMeta`, paying a metadata slot on every error in the
workspace to serve only the decode and encode surfaces. The new shape places
a non-optional `offset: usize` on each variant that can know one:

- `DecodeErrorKind::{NotEnoughBytes, InvalidField, UnexpectedMessageType,
  UnsupportedVersion, UnsupportedValue}` gain `offset: usize`
- `EncodeErrorKind::*` mirrors the same shape for encode-side errors
- `*::Other` is unchanged; producers of `Other` typically lack stream-cursor
  access and the variant exists precisely for those cases

The `in_field` dotted-path use case is dropped from this PR per the same
review: `Error::set_context` already covers it. No parallel structured
field-tracking channel is introduced.

Trait and macro changes:

- `NotEnoughBytesErr`, `InvalidFieldErr`, `UnexpectedMessageTypeErr`,
  `UnsupportedVersionErr`, `UnsupportedValueErr` all take an additional
  `offset: usize` parameter
- The five corresponding `*_err!` macros gain `at:` and `in:` prefixes for
  explicit offset and cursor-extracted offset respectively
- `OtherErr` and `other_err!` are unchanged
- `cast_length!` and `cast_int!` macros pass `0` to the new offset slot
  (the macros do not have stream-cursor access)

Call-site migration:

- All 84 affected files updated to pass an explicit offset
- Most existing call sites pass `0` (the documented "offset unknown" sentinel)
  since the cursor is not always in lexical scope at the call site
- Cursor-aware sites can opt in via the new `in: cursor` macro syntax
- A workspace sweep upgrading `at: 0` to `in: cursor` where applicable is a
  follow-up

Display output includes the offset when known:
`invalid \`field\` at offset 47: reason`

Refs #1257, #1120. Supersedes the cross-cutting `ErrorPosition` approach
that was on this branch before today's review.

Author: Greg Lamberson

crates/ironrdp-rdpdr/src/pdu/efs.rs

@@ -3044,9 +3044,11 @@ impl ServerDriveQueryVolumeInformationRequest {
             | FileSystemInformationClassLevel::FILE_FS_FULL_SIZE_INFORMATION
             | FileSystemInformationClassLevel::FILE_FS_DEVICE_INFORMATION => {}
             _ => {
-                return Err(invalid_field_err!( "ServerDriveQueryVolumeInformationRequest::decode",
+                return Err(
+                    invalid_field_err!( "ServerDriveQueryVolumeInformationRequest::decode",
                         "fs_info_class_lvl",
-                        "received invalid level", at: 0));
+                        "received invalid level", at: 0),
+                );
             }
         }