typed: Update compare algorithm to handle duplicates

[apelisse]

Same strategy as #249, still trying to address #234. Algorithm goes as follow:

1. Duplicates are treated as separate from non-duplicates items
2. Adding a duplicate to an existing item means we will remove the existing (counted as removed) and added as a duplicate (added).
3. Removing does the opposite
4. If any of the duplicated value changes, key will be counted as "modified".

Rewording:

In compare, treat duplicate keys in associative lists/sets as a separate atomic list, marked by owning just the duplicated key.

/assign @alexzielenski /cc @jpbetz

[k8s-ci-robot]

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[apelisse]

OK, I've added comments to explain what happens, hopefully that helps.

[apelisse]

OK I've added a new commit to create a new map of PEs to interface{}, and then updated the other commit to use it instead of value, which simplifies the code a tiny bit since we don't have to create the new valueinterface thingy.

[alexzielenski]

/lgtm /hold

in case you wanted to change anything else

[apelisse]

/hold

I'm good thanks!

[apelisse]

I meant /hold cancel