fix: insert full code at cursor

[abeatrix]

close: #281

Fix issue where inserted code snippets removes $s

Cause: editor.action.insertSnippet would reformat the copied text that caused the inserted text to look different

await vscode.commands.executeCommand('editor.action.insertSnippet', {
                snippet: copiedText,
            })

Fix: Use WorkspaceEdit instead to replace current selection with the copied text

See Loom for fix: https://www.loom.com/share/7c238dfeda014e00b98b51aa1b5511ea?sid=ebca9d01-7f1b-4301-97b3-0451bbdc53ab

Test Plan

Select code that has $ in it, click on explain code recipe:

• copy the code should contain the correct code snippet with all $ included
• insert the code at the cursor should contain the correct code snippet with all $ included

[toolmantim]

@abeatrix I noticed we removed the feature where you can select only a portion of the code block to insert. Was that intentional, or too tricky to keep?

[abeatrix]

I don't remember honestly lol I can take a look when I'm back tmr.

[toolmantim]

Not a priority! No one has noticed from what I can tell, but it wasn't a very visible feature. We can look at it when improving how our insert code stuff works.