THRIFT-6128: Exclude development files from the Ruby gem

[kpumuk]

The Ruby gem previously packaged spec/ directly and added test/, spec/, and benchmark/ through the obsolete test_files attribute. This change explicitly includes the Ruby runtime and native-extension sources, while retaining the README as RDoc input.

See rubygems/guides#90 for more information.

File list difference

I built gems from the pre-change and current gemspecs, then compared their data.tar.gz file lists:

diff -u \
  <(tar -xOf thrift-before.gem data.tar.gz | tar -tzf -) \
  <(tar -xOf thrift-after.gem data.tar.gz | tar -tzf -)

--- before
+++ after
@@ -1,9 +1,4 @@
 README.md
-benchmark/Benchmark.thrift
-benchmark/benchmark.rb
-benchmark/client.rb
-benchmark/server.rb
-benchmark/thin_server.rb
 ext/binary_protocol_accelerated.c
 ext/binary_protocol_accelerated.h
 ext/bytes.c
@@ -65,67 +60,3 @@
 lib/thrift/types.rb
 lib/thrift/union.rb
 lib/thrift/uuid.rb
-spec/BaseService.thrift
-spec/ExtendedService.thrift
-spec/Referenced.thrift
-spec/ThriftNamespacedSpec.thrift
-spec/ThriftSpec.thrift
-spec/base_protocol_spec.rb
-spec/base_transport_spec.rb
-spec/binary_protocol_accelerated_spec.rb
-spec/binary_protocol_spec.rb
-spec/binary_protocol_spec_shared.rb
-spec/bytes_spec.rb
-spec/client_spec.rb
-spec/compact_protocol_spec.rb
-spec/constants_demo_spec.rb
-spec/exception_spec.rb
-spec/flat_spec.rb
-spec/header_protocol_spec.rb
-spec/header_transport_spec.rb
-spec/http_client_spec.rb
-spec/json_protocol_spec.rb
-spec/multiplexed_processor_spec.rb
-spec/multiplexed_protocol_spec.rb
-spec/namespaced_spec.rb
-spec/nonblocking_server_spec.rb
-spec/processor_spec.rb
-spec/protocol_decorator_spec.rb
-spec/rack_application_spec.rb
-spec/recursion_depth_spec.rb
-spec/serializer_spec.rb
-spec/server_socket_spec.rb
-spec/server_spec.rb
-spec/socket_spec.rb
-spec/socket_spec_shared.rb
-spec/spec_helper.rb
-spec/ssl_server_socket_spec.rb
-spec/ssl_socket_spec.rb
-spec/struct_nested_containers_spec.rb
-spec/struct_spec.rb
-spec/support/header_protocol_helper.rb
-spec/thin_http_server_spec.rb
-spec/types_spec.rb
-spec/union_spec.rb
-spec/unix_socket_spec.rb
-spec/uuid_validation_spec.rb
-test/fuzz/Makefile.am
-test/fuzz/README.md
-test/fuzz/fuzz_common.rb
-test/fuzz/fuzz_parse_binary_protocol.rb
-test/fuzz/fuzz_parse_binary_protocol_accelerated.rb
-test/fuzz/fuzz_parse_binary_protocol_accelerated_harness.rb
-test/fuzz/fuzz_parse_binary_protocol_harness.rb
-test/fuzz/fuzz_parse_compact_protocol.rb
-test/fuzz/fuzz_parse_compact_protocol_harness.rb
-test/fuzz/fuzz_parse_json_protocol.rb
-test/fuzz/fuzz_parse_json_protocol_harness.rb
-test/fuzz/fuzz_roundtrip_binary_protocol.rb
-test/fuzz/fuzz_roundtrip_binary_protocol_harness.rb
-test/fuzz/fuzz_roundtrip_json_protocol.rb
-test/fuzz/fuzz_roundtrip_json_protocol_harness.rb
-test/fuzz/fuzz_tracer.rb

• Did you create an Apache Jira ticket? (THRIFT-6128)
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit? (not required, but preferred)
• Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• This change involves code, so [skip ci] does not apply.