Encoding issue with interned symbols

[ahorek]

Environment Information
jruby 9.4.1.0-SNAPSHOT (3.1.0) 2023-02-04 ec0164c Java HotSpot(TM) 64-Bit Server VM 15.0.2+7-27 on 15.0.2+7-27 +jit [x86_64-linux]

originally reported msgpack/msgpack-ruby#248 and my (incorrect) attempt for a workaround #7618

Expected Behavior

source = "fée"
iso_symbol = source.force_encoding(Encoding::ISO_8859_1).to_sym
p iso_symbol.encoding # => Encoding::ISO_8859_1
p iso_symbol.object_id # => 60
binary_symbol = source.force_encoding(Encoding::BINARY).to_sym
p binary_symbol.encoding # => Encoding:ASCII-8BIT
p binary_symbol.object_id # => 80

Actual Behavior

source = "fée"
iso_symbol = source.force_encoding(Encoding::ISO_8859_1).to_sym
p iso_symbol.encoding # => Encoding::ISO_8859_1
p iso_symbol.object_id # => 4000
binary_symbol = source.force_encoding(Encoding::BINARY).to_sym
p binary_symbol.encoding # => Encoding:ISO-8859-1
p binary_symbol.object_id # => 4000

non-ascii symbols with the same byte representation are shared even if the encoding is different.