Problem:
When CONFIG_DEBUG_MM_HEAPINFO is enabled, the memory allocation node
stores the PID of the currently running task to identify the memory
owner. This causes incorrect attribution when kernel modules allocate
memory on behalf of other tasks.

For example, when the log_dump test application runs, it triggers
logging via log_dump_save() which internally calls kmm_malloc(). The
allocated memory node incorrectly stores the test application's PID
instead of the log_dump kernel thread's PID, causing false alerts in
memory debugging.

Solution:
Add a new API heapinfo_set_pid() and corresponding DEBUG_SET_PID() macro
that allows kernel modules to explicitly set their PID on allocated
memory nodes after the allocation.

Changes:
1. mm/mm_heap/mm_heapinfo_utils.c: Add heapinfo_set_pid() function
2. include/tinyara/mm/mm.h: Add DEBUG_SET_PID() macro and declaration
3. kernel/log_dump/log_dump.c: Use DEBUG_SET_PID() to set correct PID
   for all kmm_malloc() allocations

Design Decisions:
- Follow existing pattern of DEBUG_SET_CALLER_ADDR() for consistency
- Use a no-op macro when CONFIG_DEBUG_MM_HEAPINFO is disabled to avoid
  any overhead in release builds
- Store log_dump thread's PID at initialization and reuse it for all
  subsequent allocations
- The API is generic and can be used by other kernel modules with
  similar requirements

Impact:
- Memory allocated by log_dump module is now correctly attributed to
  the log_dump kernel thread
- No impact when CONFIG_DEBUG_MM_HEAPINFO is not enabled
- API is reusable by other kernel modules that need similar functionality

TC1: Flat build (rtl8730e)
log Dump pid = 13

13 |     4 | 10216 |     12496 |    331808 | log_dump()

0x601755f0 |     4128 |   A    | 0x e025bf3 |  13   |
0x60176610 |     4128 |   A    | 0x e025bf3 |  13   |

TC2: Loadable build (rtl8730e)
log dump pid: 15

15 |     4 | 10216 |     12496 |    331808 |   kernel | log_dump()

0x603a57e0 |     4128 |   A    | 0x e023003 |  15   |
0x603a6800 |     4128 |   A    | 0x e023003 |  15   |
0x603a7820 |     4128 |   A    | 0x e023003 |  15   |

Signed-Off By: Vivek Jain (vivek1.j@samsung.com)