[APX403]

Closes #2518

Psych.safe_dump has no signature, so type checkers that read these signatures do not know about it (castwide/solargraph#959):

$ rbs -r psych method --singleton Psych safe_dump
Cannot find method: safe_dump

Psych.load and Psych.load_file also lack the keywords load has taken since psych 4 made it safe by default: permitted_classes:, permitted_symbols: and aliases:. A YAML file with aliases or dates needs them, as in YAML.load_file("config/database.yml", aliases: true).

This adds:

• Psych.safe_dump, with the overloads of Psych.dump plus permitted_classes:, permitted_symbols: and aliases:
• permitted_classes:, permitted_symbols:, aliases: and strict_integer: to Psych.load and Psych.load_file
• strict_integer: to Psych.safe_load, Psych.safe_load_file and Psych.unsafe_load_file, which Psych.unsafe_load already declares
• stringify_names: to Psych.dump and Psych.safe_dump

The safe_dump comment is generated by rake annotate. parse_symbols: (psych 5.3) is left out because the stdlib tests run with psych 4.0.6, which goodcheck pins in Gemfile.lock and which does not have it.

[ksss]

Thanks!