Improve syntax error reporting for graphql macro

[OlegIlyenko]

Ideally the error position should point out the correct position inside of the GraphQL string.

Here is an example of error + position that should be reported:

[error] SchemaComparatorSpec.scala:77: Invalid input "typ ", expected OperationDefinition, FragmentDefinition or TypeSystemDefinition
[error]         typ Foo {
[error]         ^
[error] one error found
[error] (test:compileIncremental) Compilation failed

But currently it's reported as:

[error] SchemaComparatorSpec.scala:68: Invalid input "typ ", expected OperationDefinition, FragmentDefinition or TypeSystemDefinition (line 10, column 9):
[error]         typ Foo {
[error]         ^
[error]       graphql"""
[error]       ^
[error] one error found
[error] (test:compileIncremental) Compilation failed

which is quite confusing and points at the wrong location.