Fix wrong location issue in "string" interpolation

String interpolation issue like #3524.
The location of token in 1 double quoted string is broken. 

Starting with `\n`:
```
"
#{a}
b
#{c}
"
```

The location is:
```
[ 'IDENTIFIER',
  'a',
  { first_line: 1, first_column: 1, last_line: 1, last_column: 1 } ]
[ 'IDENTIFIER',
  'c',
  { first_line: 3, first_column: 1, last_line: 3, last_column: 1 } ]
```

This patch makes the location collect position:
```
[ 'IDENTIFIER',
  'a',
  { first_line: 1, first_column: 2, last_line: 1, last_column: 2 } ]
[ 'IDENTIFIER',
  'c',
  { first_line: 3, first_column: 2, last_line: 3, last_column: 2 } ]
```

I added 4 tests for this problem, and added 1 test for #3524 just in case.