mpl2: group snap functionalities in a class and avoid snapping twice

[AcKoucher]

Changes:

• Prepare mpl2 for removing the dbu <--> micron internal methods of conversion for the new dbBlock ones
• Make place_macro not relying on mpl2 internals anymore
• Avoid snapping when updating odb the first time

The minimal changes in macro_only test results are due to removing the unneeded snap.

If the approach is ok I'll run CI

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[maliberty]

go ahead w/CI

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[AcKoucher]

Opened #2036 for the metrics. So this should be good to merge.

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"