fix: backward compatibility broken for Dataform v2.x

[ashish10alex]

This PR

• Fixes the broken backward compatibility of the extension when working with Dataform projects using version 2.x . Dataform CLI v2.x adds a json block showing some kind of logging which no longer exists in v3. This PR first tries to parse the JSON block as is, if that gives an error we read the JSON block assuming it has multiple blocks and pick the first block as the block which has Datfaorm metadata. See screenshots below to see the additional json block at index [0].
• Improve error messages when user tries to use v2.x cli with a v3.x project

Tests

• Extension works as expected for both v2.x v3.x projects. - compiles, shows compilation errors and dry run errors as before

NOTE
The tests for v2.x were largely done for v2.9 but the extra JSON block did seem to be there for one other v2.x version as well.