This patch adds a global `--no-integrate-operation` flag that prevents
integration/publishing of most operations, including the ones created by
`snapshot_working_copy()` and `finish_transaction()`. The operations
are still created as usual.
We provide `jj op integrate` to manually reintegrate operations created by
commands with this flag enabled.
Closes#2562
Co-authored-by: Martin von Zweigbergk <martinvonz@google.com>