coredump: Add config for capturing thread data in core dump

Update core dump file format to support a new section which contains
metadata about threads necessary for debugging.

Define configs to capture that metadata and include it in the dumps
when enabled.

Update documentation to reflect the changes.

Signed-off-by: Mark Holden <mholden@meta.com>

doc/services/debugging/coredump.rst

@@ -30,6 +30,13 @@ Here are the choices regarding memory dump:
   walking the stack in the debugger. Use this only if absolute minimum of data
   dump is desired.
 
+* ``DEBUG_COREDUMP_MEMORY_DUMP_THREADS``: Dumps the thread struct and stack of all
+  threads and all data required to debug threads.
+
+* ``DEBUG_COREDUMP_MEMORY_DUMP_LINKER_RAM``: Dumps the memory region between
+  _image_ram_start[] and _image_ram_end[]. This includes at least data, noinit,
+  and BSS sections. This is the default.
+
 Additional memory can be included in a dump (even with the "DEBUG_COREDUMP_MEMORY_DUMP_MIN"
 config selected) through one or more :ref:`coredump devices <coredump_device_api>`
 
@@ -244,7 +251,8 @@ File Format
 ***********
 
 The core dump binary file consists of one file header, one
-architecture-specific block, and multiple memory blocks. All numbers in
+architecture-specific block, zero or one threads metadata block(s),
+and multiple memory blocks. All numbers in
 the headers below are little endian.
 
 File Header
@@ -315,6 +323,36 @@ to the target architecture (e.g. CPU registers)
      - ``uint8_t[]``
      - Contains target architecture specific data.
 
+Threads Metadata Block
+---------------------------
+
+The threads metadata block contains the byte stream of data necessary
+for debugging threads.
+
+.. list-table:: Threads Metadata Block
+   :widths: 2 1 7
+   :header-rows: 1
+
+   * - Field
+     - Data Type
+     - Description
+   * - ID
+     - ``char``
+     - ``T`` to indicate this is a threads metadata block.
+   * - Header version
+     - ``uint16_t``
+     - Identify the version of the header. This needs to be incremented
+       whenever the header struct is modified. This allows parser to
+       reject older header versions so it will not incorrectly parse
+       the header.
+   * - Number of bytes
+     - ``uint16_t``
+     - Number of bytes following the header which contains the byte stream
+       for target data.
+   * - Byte stream
+     - ``uint8_t[]``
+     - Contains data necessary for debugging threads.
+
 Memory Block
 ------------