Position correctly when inserting before another block (from the flyout)

[rachel-fenichel]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide

The details

Resolves

Previously the block stack would move to 100, 100 on the workspace if the new block was being inserted at the start.

Proposed Changes

Use the same code that we use to solve this problem for insertion markers.
I moved the helper function and changed its signature because it had an unnecessary param before. That's the first commit. The second commit uses it.
Remove extra connect calls in insertBlock--connect moves the orphanBlock around internally.

Reason for Changes

Blocks need to stay in the same place as new blocks are connected.

Test Coverage

Tested in the playground.

Additional information

I had to add a call to render so that the new block's connection positions are correct internally. That I expected. I also had to explicitly set the connections to not be hidden, which I didn't expect. The connections are hidden in domToBlock and unhidden in a timeout, for speed when creating large block stacks. But if the connections are still hidden when I move the block, Erik's new code in #2003 makes the child block disappear.

[RoboErikG]

lgtm

[rachel-fenichel]

Lint errors in astnode_test, probably from recent rebase. I'll fix indentation and then merge.