Add extra format selection tests

We currently don't have any tests ensuring that other things inside braces don't get formatted when we select a portion of a braced list

Tests 1 and 3 here should format the whole braced expressions, but tests 2 and 4 should only format the selection itself

            #[rustfmt::skip]
            let (doc, range) = TextDocument::doodle_and_range(
"0+0
1+1
<<{
  2+2>>
  3+3
}
4+4
",
            );
            let output = client.format_document_range(&doc, range);
            insta::assert_snapshot!(output);

            #[rustfmt::skip]
            let (doc, range) = TextDocument::doodle_and_range(
"0+0
1+1
{<<
  2+2>>
  3+3
}
4+4
",
            );
            let output = client.format_document_range(&doc, range);
            insta::assert_snapshot!(output);

            #[rustfmt::skip]
            let (doc, range) = TextDocument::doodle_and_range(
"0+0
1+1
{
  2+2
  <<3+3
}>>
4+4
",
            );
            let output = client.format_document_range(&doc, range);
            insta::assert_snapshot!(output);

            #[rustfmt::skip]
            let (doc, range) = TextDocument::doodle_and_range(
"0+0
1+1
{
  2+2
  <<3+3
>>}
4+4
",
            );
            let output = client.format_document_range(&doc, range);
            insta::assert_snapshot!(output);

Start by locating the existing tests around TextDocument::doodle_and_range and client.format_document_range. Add the four braced-list selection cases shown in the issue and update their insta snapshots so tests 1 and 3 format the whole expression while tests 2 and 4 format only the selection.