place alignas() before lifetime specifiers

[mumbleskates]

This patch fixes a compilation bug introduced in 821b073.

When the constinit keyword is available (such as in C++20), putting the alignas attribute after ABSL_CONST_INIT is an error:

ERROR: /home/widders/.cache/bazel/_bazel_widders/25f0d335ca0e01a2fd74c60e90175e8f/external/com_google_protobuf/src/google/protobuf/compiler/java/BUILD.bazel:44:11: Compiling src/google/protobuf/compiler/java/generator_factory.cc failed: (Exit 1): clang failed: error executing command /usr/lib/llvm-16/bin/clang -U_FORTIFY_SOURCE -fstack-protector -Wall -Wthread-safety -Wself-assign -Wunused-but-set-parameter -Wno-free-nonheap-object -fcolor-diagnostics -fno-omit-frame-pointer -g0 ... (remaining 64 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
In file included from external/com_google_protobuf/src/google/protobuf/compiler/java/generator_factory.cc:35:
In file included from bazel-out/k8-opt-exec-2B5CBBC6/bin/external/com_google_protobuf/src/google/protobuf/compiler/java/_virtual_includes/java/google/protobuf/compiler/java/context.h:38:
In file included from bazel-out/k8-opt-exec-2B5CBBC6/bin/external/com_google_protobuf/src/google/protobuf/compiler/java/_virtual_includes/names_internal/google/protobuf/compiler/java/helpers.h:45:
In file included from bazel-out/k8-opt-exec-2B5CBBC6/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_nowkt/google/protobuf/descriptor.pb.h:25:
In file included from bazel-out/k8-opt-exec-2B5CBBC6/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/arena.h:53:
bazel-out/k8-opt-exec-2B5CBBC6/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/arena_impl.h:584:19: error: an attribute list cannot appear here
  ABSL_CONST_INIT alignas(
                  ^~~~~~~~
1 error generated.

Therefore, it should be ordered as

1. always attribute-like (alignas)
2. sometimes attributes (ABSL_CONST_INIT, which may be a lifetime specifier or an attribute)
3. lifetime specifiers (static)
4. type etc.

Where it currently is it may be in the midst of lifetime specifiers, and if it is moved to the right it syntactically applies to the type rather than the whole declaration which is also invalid.

If this ordering could not be resolved for all cases it could also be moved to the end, after the name being declared, but we don't need to do that here.

[jorgbrown]

Thanks!! Just one nit about spacing.

[jorgbrown]

LGTM