Nested conditionals

[Janther]

The current parser interprets nested ternaries in a different way as the compiler does.

// Input
a ? b : c ? d : e;

// Wrong interpretation
(a ? b : c) ? d : e;

// Correct interpretation
a ? b : (c ? d : e);

Both AST print the same code in prettier-plugin-solidity thus we haven't noticed this bug in the past.

[fvictorio]

Thanks @Janther. I think it's better to fix this in the grammar itself. I did that in solidity-parser/antlr@37f9f9c and then undid your changes to use that instead. The tests you added still pass.

If you are ok with this, I will merge and release it.

[Janther]

Much more elegant