Add support for IDLE Thread stack allocator

Add a stack allocator hook specifically for allocation of IDLE thread stacks.
This allows the user to decide if IDLE thread stacks are statically allocated
or handled by the same custom allocator mechanism as other thread stacks.

Closes #4524.

spec/build/cpukit/librtemscpu.yml

@@ -1527,6 +1527,7 @@ source:
 - cpukit/score/src/semaphore.c
 - cpukit/score/src/smpbarrierwait.c
 - cpukit/score/src/stackallocator.c
+- cpukit/score/src/stackallocatorforidle.c
 - cpukit/score/src/stackallocatorfree.c
 - cpukit/score/src/stackallocatorinit.c
 - cpukit/score/src/thread.c

spec/build/testsuites/sptests/grp.yml

@@ -395,6 +395,10 @@ links:
   uid: spstkalloc
 - role: build-dependency
   uid: spstkalloc02
+- role: build-dependency
+  uid: spstkalloc03
+- role: build-dependency
+  uid: spstkalloc04
 - role: build-dependency
   uid: spsysinit01
 - role: build-dependency

spec/build/testsuites/sptests/spstkalloc03.yml

@@ -0,0 +1,19 @@
+SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
+build-type: test-program
+cflags: []
+copyrights:
+- Copyright (C) 2030 embedded brains GmbH (http://www.embedded-brains.de)
+cppflags: []
+cxxflags: []
+enabled-by: true
+features: c cprogram
+includes: []
+ldflags: []
+links: []
+source:
+- testsuites/sptests/spstkalloc03/init.c
+stlib: []
+target: testsuites/sptests/spstkalloc03.exe
+type: build
+use-after: []
+use-before: []

spec/build/testsuites/sptests/spstkalloc04.yml

@@ -0,0 +1,19 @@
+SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
+build-type: test-program
+cflags: []
+copyrights:
+- Copyright (C) 2040 embedded brains GmbH (http://www.embedded-brains.de)
+cppflags: []
+cxxflags: []
+enabled-by: true
+features: c cprogram
+includes: []
+ldflags: []
+links: []
+source:
+- testsuites/sptests/spstkalloc04/init.c
+stlib: []
+target: testsuites/sptests/spstkalloc04.exe
+type: build
+use-after: []
+use-before: []