Add Span.h to a source_set that tracks its dependencies.

This requires that those dependencies be separate things that are not the entire
"support" library, because some things need Span but can't depend on all of
"support".  Maybe these should just all be lumped into "support_core"... but
then why are these things in support/ and not core/ (which are very much "these
are the same thing, but we are going to pretend the are not).

Fixes #29490

src/lib/support/BUILD.gn

@@ -73,6 +73,40 @@ source_set("attributes") {
   ]
 }
 
+source_set("logging_header") {
+  sources = [ "logging/CHIPLogging.h" ]
+
+  public_deps = [
+    ":attributes",
+    ":logging_constants",
+    "${chip_root}/src/lib/core:chip_config_header",
+  ]
+
+  if (chip_pw_tokenizer_logging) {
+    public_deps += [ "${dir_pw_tokenizer}" ]
+  }
+}
+
+source_set("codeutils") {
+  sources = [
+    "CodeUtils.h",
+  ]
+
+  public_deps = [
+    ":attributes",
+    ":logging_header",
+    "${chip_root}/src/lib/core:chip_config_header",
+    "${chip_root}/src/lib/core:error",
+    "${nlassert_root}:nlassert",
+  ]
+}
+
+source_set("span") {
+  sources = [ "Span.h" ]
+
+  public_deps = [ ":codeutils" ]
+}
+
 source_set("chip_version_header") {
   sources = get_target_outputs(":gen_chip_version")
 
@@ -102,7 +136,6 @@ static_library("support") {
     "CHIPMemString.h",
     "CHIPPlatformMemory.cpp",
     "CHIPPlatformMemory.h",
-    "CodeUtils.h",
     "DLLUtil.h",
     "DefaultStorageKeyAllocator.h",
     "Defer.h",
@@ -141,7 +174,6 @@ static_library("support") {
     "ZclString.cpp",
     "ZclString.h",
     "logging/CHIPLogging.cpp",
-    "logging/CHIPLogging.h",
     "verhoeff/Verhoeff.cpp",
     "verhoeff/Verhoeff.h",
     "verhoeff/Verhoeff10.cpp",
@@ -168,7 +200,10 @@ static_library("support") {
   public_deps = [
     ":attributes",
     ":chip_version_header",
+    ":codeutils",
     ":logging_constants",
+    ":logging_header",
+    ":span",
     "${chip_root}/src/lib/core:chip_config_header",
     "${chip_root}/src/lib/core:error",
     "${chip_root}/src/platform:platform_buildconfig",

src/platform/Darwin/BUILD.gn

@@ -137,10 +137,9 @@ static_library("logging") {
   ]
 
   deps = [
-    "${chip_root}/src/lib/core:chip_config_header",  # for lib/support/Span.h
     "${chip_root}/src/lib/support:attributes",
     "${chip_root}/src/lib/support:logging_constants",
-    "${nlassert_root}:nlassert",  # for lib/support/Span.h
+    "${chip_root}/src/lib/support:span",
   ]
 
   configs += [ "${chip_root}/src:includes" ]