Revert flattened error hierarchies back to original Error struct + ErrorKind enum structure

Co-authored-by: benhillis <[email protected]>

Author: Copilot

Cargo.lock

@@ -2879,7 +2879,6 @@ dependencies = [
  "igvm_defs",
  "inspect",
  "memory_range",
- "thiserror 2.0.12",
  "tracing",
 ]
 
@@ -2975,7 +2974,6 @@ dependencies = [
  "bitfield-struct 0.10.1",
  "open_enum",
  "static_assertions",
- "thiserror 2.0.12",
  "zerocopy 0.8.24",
 ]
 

openhcl/host_fdt_parser/Cargo.toml

@@ -19,7 +19,6 @@ inspect = { workspace = true, optional = true }
 
 arrayvec.workspace = true
 igvm_defs.workspace = true
-thiserror.workspace = true
 tracing = { workspace = true, optional = true }
 
 [lints]