Add insertion flags conversion function to ease deprecation

This adds a simple way to convert a set of insertion parameters to a
real InsertionParams object.

Bug: 1524018
Change-Id: I9d2521cf6b2d19217d4e9d019c7019571d2ac316
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5258508
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Louis Romero <lpromero@google.com>
Reviewed-by: Asami Doi <asamidoi@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Quentin Pubert <qpubert@google.com>
Cr-Commit-Position: refs/heads/main@{#1256684}