Remove the legacy thread annotation spellings

The legacy thread annotations were spellings that were not prefixed
with ABSL_ and caused conflicts with other libraries. These spellings
have been removed by default for a while, but could have been added
back with the temporary compile flag
-DABSL_LEGACY_THREAD_ANNOTATIONS. This change completely removes the
legacy spellings.

If you were relying on the legacy spellings, the fix is
straightforward. Simply add the ABSL_ prefix. For example,
GUARDED_BY() becomes ABSL_GUARDED_BY().

PiperOrigin-RevId: 560874026
Change-Id: Id072e67435472220ea4f43ccbf267028c13feba7

CMake/AbseilDll.cmake

@@ -44,7 +44,6 @@ set(ABSL_INTERNAL_DLL_FILES
   "base/internal/spinlock_wait.h"
   "base/internal/sysinfo.cc"
   "base/internal/sysinfo.h"
-  "base/internal/thread_annotations.h"
   "base/internal/thread_identity.cc"
   "base/internal/thread_identity.h"
   "base/internal/throw_delegate.cc"

absl/base/BUILD.bazel

@@ -161,7 +161,6 @@ cc_library(
 cc_library(
     name = "core_headers",
     srcs = [
-        "internal/thread_annotations.h",
     ],
     hdrs = [
         "attributes.h",

absl/base/CMakeLists.txt

@@ -156,7 +156,6 @@ absl_cc_library(
     "optimization.h"
     "port.h"
     "thread_annotations.h"
-    "internal/thread_annotations.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS

absl/base/thread_annotations.h

@@ -36,8 +36,6 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
-// TODO(mbonadei): Remove after the backward compatibility period.
-#include "absl/base/internal/thread_annotations.h"  // IWYU pragma: export
 
 // ABSL_GUARDED_BY()
 //