Add SDK support for device memory inspection

[floitsch]

This extracts the SDK/runtime portion of the device-memory inspector work so the required SDK surface can be reviewed independently of the tool itself.

Included

• source-level parameter names and local stack-slot lifetimes in snapshot debug metadata
• an experimental privileged ESP32 terminal UART memory-dump primitive
• optional stable VM-state transition checkpoints (TOIT_VM_STATE_CHECKPOINTS)
• GC-metadata and Bluetooth allocator attribution
• snapshot/memory-report decoding support for the new metadata and tags

Deliberately excluded

• the inspector model, query API, server, and HTML viewer
• UART/QEMU acquisition clients and capture fixtures
• the GDB RSP package
• the special capture boot image
• build-time GDB/ELF extraction and inspector envelope entries

The last item should return as generic ELF/DWARF and envelope metadata support rather than make the SDK build import the inspector package.

This is 28 files, 1,357 insertions, and 44 deletions. The low-level ESP32 dump is isolated in device_memory_dump_esp32.cc; os_esp32.cc gains only three allocation-accounting lines. The changes are split into snapshot-metadata and ESP32-runtime commits.

RISC-V allocation tagging depends on #3183, which is intentionally a separate PR and can be merged independently.

Validation

• host VM/CLI compilation reached the package-sync stage successfully (package sync itself is unavailable in the sandbox cache)
• frame-debug snapshot decode test passed
• frame-debug toitp presentation test passed
• the split ESP32 dump, primitive, and os_esp32.cc translation units cross-compiled successfully
• the renamed VM-state checkpoint implementation and all changed consumers compiled successfully
• git diff --check passed