Add flags to speed up menu generation

This is draft related to ATR-26996 It is an attempt to speed up menu generation by avoiding remerge of entire CAs that were seen. I did measure it using time utility with the test as is and after including also jets. Unless there is better place where such optimisation can be added the number of saved merges is quite small and the effect is negligible! Certainly not worth additional feature that would put us in need to revalidate menu generation repetitively.

Tagging for info: @fpastore @tamartin @khoo @fwinkl

It also address missing CA merges issue from !61689 (merged)