[Drift] Add support for Java optional to IDL generator

[shangm2]

1. Add support for Java optional to IDL generator
2. Optional field will be marked as optional even without requireness annotation

[NikhilCollooru]

Ideally it would be great if we have test that does the entire loop
Java class --> thrift idl --> Cpp/Java class.
that way we can catch any bugs like spelling mistake etc,.

[shangm2]

Ideally it would be great if we have test that does the entire loop Java class --> thrift idl --> Cpp/Java class. that way we can catch any bugs like spelling mistake etc,.

Chatted offline. the current test is good enough.

[arhimondr]

Could you please check if primitive flavours of Optional work (e.g.: OptionalInt, OptionalLong, OptionalDouble, etc.)

[shangm2]

@arhimondr primitive flavours of Optional works if their corresponding codecs are loaded, pls see this pr #112