[Feature] begin/end less range expression

[taichi-ishitani]

I'd like to introduce begin/end less range expression. This is an example:

var a: logic<4>;
var b: logic;
b = inside a {..8};  // a inside {[$:7}];
b = inside a {..=8}; // a inside {[$:8}];
b = inside a {8..};  // a inside {[8:$]};
b = inside a {8..=}; // a inside {[8:$]};

I think begin/end less range expression is useful when it is used with other range expressions like below.

var a: logic<4>;
var b: logic;
b = inside a {..1, 3..=4, 14..};