Reduce object allocation for record type

[ksss]

Repro

# Gemfile
source "https://rubygems.org"
gem 'aws-sdk-quicksight' # It has many record types

$ bundle exec rbs collection init
$ bundle exec rbs collection install

# t.rb
require 'rbs'
require 'rbs/cli'
require 'memory_profiler'
report = MemoryProfiler.report do
  loader = RBS::CLI::LibraryOptions.new.loader
  env = RBS::Environment.from_loader(loader)
  env.resolve_type_names
end
report.pretty_print

Before

Total allocated: 593146847 bytes (6288468 objects)
Total retained:  239940 bytes (3582 objects)
...
allocated memory by location
-----------------------------------
 301030072  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/parser_aux.rb:20
  53040880  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:529
  42449400  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:680
  36932720  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:530
  24652000  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:596
  24599520  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:374
  19889959  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/environment_loader.rb:164

After

Total allocated: 555155855 bytes (5427912 objects)
Total retained:  239940 bytes (3582 objects)
...
allocated memory by location
-----------------------------------
 301030072  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/parser_aux.rb:20
  42449400  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:687
  24652000  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:603
  24599520  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:374
  19980288  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:529
  19889959  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/environment_loader.rb:164
  19721600  /Users/yuki.kurihara/src/github.com/ksss/rbs/lib/rbs/types.rb:530

[soutaro]

👍