build: update flatbuffers dependency to v23.5.26

Update the third_party flatbuffers library to v23.5.26, the
current version in upstream TF. Synchronize the override BUILD
and build_defs.bzl files with those from upstream TF at
e4485c98eae.

Also update the Makefile build, which downloads flatbuffers
separately. Rebase the patch applied to the download.

Regenerate the generated-and-checked-in schemas (see
ci/sync_from_upstream_tf.sh), because they are stamped with the
version of the flatbuffers library, and fail a static_assert if
they are built with a different version of flatbuffers than they
were generated with.

BUG=unsuccessful attempt to fix warning in #2183

Author: rkuester

tensorflow/lite/micro/tools/make/flatbuffers.patch

@@ -1,5 +1,5 @@
 diff --git a/include/flatbuffers/base.h b/include/flatbuffers/base.h
-index a5ac10d..371b6fd 100644
+index 5c4cae79..1a631641 100644
 --- a/include/flatbuffers/base.h
 +++ b/include/flatbuffers/base.h
 @@ -1,6 +1,16 @@
@@ -20,10 +20,10 @@ index a5ac10d..371b6fd 100644
 
  // If activate should be declared and included first.
 diff --git a/include/flatbuffers/default_allocator.h b/include/flatbuffers/default_allocator.h
-index 8b173af..975d938 100644
+index d4724122..975d9380 100644
 --- a/include/flatbuffers/default_allocator.h
 +++ b/include/flatbuffers/default_allocator.h
-@@ -39,26 +39,20 @@ class DefaultAllocator : public Allocator {
+@@ -39,24 +39,18 @@ class DefaultAllocator : public Allocator {
  // This is to avoid having a statically or dynamically allocated default
  // allocator, or having to move it between the classes that may own it.
  inline uint8_t *Allocate(Allocator *allocator, size_t size) {
@@ -52,15 +52,11 @@ index 8b173af..975d938 100644
  }
 
  }  // namespace flatbuffers
- 
--#endif  // FLATBUFFERS_DEFAULT_ALLOCATOR_H_
-\ No newline at end of file
-+#endif  // FLATBUFFERS_DEFAULT_ALLOCATOR_H_
 diff --git a/include/flatbuffers/flexbuffers.h b/include/flatbuffers/flexbuffers.h
-index 89f3f30..6e6d0b3 100644
+index 8e8cac14..52dae316 100644
 --- a/include/flatbuffers/flexbuffers.h
 +++ b/include/flatbuffers/flexbuffers.h
-@@ -496,9 +496,24 @@ class Reference {
+@@ -495,9 +495,24 @@ class Reference {
            return static_cast<double>(ReadUInt64(Indirect(), byte_width_));
          case FBT_NULL: return 0.0;
          case FBT_STRING: {
@@ -86,10 +82,10 @@ index 89f3f30..6e6d0b3 100644
          case FBT_VECTOR: return static_cast<double>(AsVector().size());
          case FBT_BOOL:
 diff --git a/include/flatbuffers/util.h b/include/flatbuffers/util.h
-index 93a39de..1cd4e8f 100644
+index 1ccf3517..34a75193 100644
 --- a/include/flatbuffers/util.h
 +++ b/include/flatbuffers/util.h
-@@ -24,6 +24,12 @@
+@@ -23,6 +23,12 @@
  #include "flatbuffers/base.h"
  #include "flatbuffers/stl_emulation.h"
 
@@ -102,4 +98,3 @@ index 93a39de..1cd4e8f 100644
  #ifndef FLATBUFFERS_PREFER_PRINTF
  #  include <iomanip>
  #  include <sstream>
- 

tensorflow/lite/micro/tools/make/flatbuffers_download.sh

@@ -54,17 +54,17 @@ DOWNLOADED_FLATBUFFERS_PATH=${DOWNLOADS_DIR}/flatbuffers
 if [ -d ${DOWNLOADED_FLATBUFFERS_PATH} ]; then
   echo >&2 "${DOWNLOADED_FLATBUFFERS_PATH} already exists, skipping the download."
 else
-  ZIP_PREFIX="a66de58af9565586832c276fbb4251fc416bf07f"
+  ZIP_PREFIX="v23.5.26"
   FLATBUFFERS_URL="https://github.com/google/flatbuffers/archive/${ZIP_PREFIX}.zip"
-  FLATBUFFERS_MD5="51a7a96747e1c33eb4aac6d52513a02f"
+  FLATBUFFERS_MD5="e87e8acd8e2d53653387ad78720316e2"
 
   TEMPDIR="$(mktemp -d)"
   TEMPFILE="${TEMPDIR}/${ZIP_PREFIX}.zip"
   wget ${FLATBUFFERS_URL} -O "$TEMPFILE" >&2
   check_md5 "${TEMPFILE}" ${FLATBUFFERS_MD5}
 
   unzip -qo "$TEMPFILE" -d "${TEMPDIR}" >&2
-  mv "${TEMPDIR}/flatbuffers-${ZIP_PREFIX}" ${DOWNLOADED_FLATBUFFERS_PATH}
+  mv "${TEMPDIR}/flatbuffers-${ZIP_PREFIX#v}" ${DOWNLOADED_FLATBUFFERS_PATH}
   rm -rf "${TEMPDIR}"
 
   pushd ${DOWNLOADED_FLATBUFFERS_PATH} > /dev/null