Insertion tool should wait until symbols are available

Sometimes the Insertion Symbol Check fails because we created the insertion too soon after the build completed. https://dev.azure.com/devdiv/DevDiv/_git/VS/pullrequest/333559

It would be nice if the insertion tool could work around this by waiting for the symbols to become available before going through with creating the insertion.

Start by examining the insertion tool's flow around the Insertion Symbol Check and the build-completion timing described in the issue. Review the referenced pull request for context; done means the tool waits for symbols to become available before creating the insertion and avoids the reported failure.

Written by the indexing model from the issue text.