fix(fmt): preserve line comments in blocks

[rkrasiuk]

Motivation

on the block level, simple line comments get formatted as prefix comments

Example with old behavior

before formatting:

contract Format {
   constructor() {
       uint256 a = 1;

       // TODO: do this and that
   }
}

after first run:

contract Format {
   constructor() {
       uint256 a = 1;

       // TODO: do this and that
   }
}

after second run:

contract Format {
   constructor() {
       uint256 a = 1; // TODO: do this and that
   }
}

Solution

preserve the line comments on the block level

[mattsse]

lgtm

clippy lints fixed on master