feat(icx-asset): add `--no-delete` option to `sync` command

[olaszakos]

Description

Adds --no-delete option to support the use case where the asset canister should keep all old assets.

How Has This Been Tested?

I added a new e2e test to e2e/tests-icx-asset/icx-asset.bash

Checklist:

• [x] The title of this PR complies with Conventional Commits.
• [ ] I have edited the CHANGELOG accordingly.
• [ ] I have made corresponding changes to the documentation.