add upgrade code for persistence layer upgrades

[sudden6]

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This is the rest of the changes for finishing #5410

These are not yet final so don't waste your time reviewing it.

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This change is 

[sudden6]

Based on #5440 this integrates the upgrade code to move the persistent data to the new places.

Once merged, this fixes #5410

[Diadlo]

Version strings can be compared wrong. "10.1" < "1.2"

[sudden6]

I suspected this solution is to simple to be good -_-

[Diadlo]

I suggest instead of hardcored if(curVersion < "1.17.0" && !upgradeFrom_1_16_3()) + if(curVersion < "1.18.0" && !upgradeFrom_1_17_0()) etc. use something like this

struct Version {
    int major, minor, patch;
    bool operator<(const Version& other);
};

class IVersionUpdater {
    Version getVersion() virtual = 0;
    bool apply() virtual = 0;
};

class VersionUpdater_1_16_3 : IVersionUpdater {
    Version getVersion() { return {1, 16, 3}; }
    bool apply() { /* something */ }
};

std::vector<IVersionUpdater> PersistenceUpgrader::updates = {
    VersionUpdater_1_16_3(),
    VersionUpdater_1_17(), 
    /* ... */
};

bool PersistenceUpgrader::doUpdate() {
    for (auto update : updates) {
        if (update.getVersion() < currentVersion) {
            if (!update.apply()) {
                return false;
            }
        }
    }
}

ADDED: Instead of abstract class IVersionUpdater with extra memory allocation etc., you can use

struct VersionUpdater {
    Version version;
    std::function<void()> apply;
};


std::vector<VersionUpdater> PersistenceUpgrader::updates = {
    { {1, 16, 3}, apply_from_1_16_3 },
    { {1, 17, 0}, apply_from_1_17_0 },
    /* ... */
};

[Diadlo]

Or even better use not version, but incremental number. Otherwise you can't do two persistence update in one release. In this case you just need to apply PersistenceUpgrader::updates from currentId until the end

[sudden6]

Thanks for the feedback, I'll rework this and then update it.