Avoid sending evaluated sources until they're first referenced on DAP

[connor4312]

In a Blazor case, there can be a ton of generated sources which can clog up the UI. We can improve this by omitting evaluated scripts from the protocol until the first time they're referenced.

[connor4312]

Verification, have a script like:

const logAdd = new Function('a', 'b', 'console.log(a + b);');
const returnAdd = new Function('a', 'b', 'a + b');
eval('1234');

debugger;
logAdd(2, 3);

debugger;
returnAdd(4, 5);

• Debug it
• On the first debugger statement, look in the "Loaded Sources" view. Verify there's no <eval> node there
• Continue
• Verify there's now an eval script and that the log in the Debug Console has a clickable source location attached
• Step into returnAdd
• Verify there's a second <eval> node and that you get what you expect when doing the step in