HO to enable taking app memory size from SM input

[yamingk]

I believe we should fix this: https://github.com/eBay/HomeObject/blob/main/src/lib/homestore_backend/hs_homeobject.cpp#L125
Ideally the app_mem_size should come from SM booting parameter by consulting the pod spec Memory Limit.

Maybe something like:

class HomeObjectApplication { 
...
    virtual uint64_t app_mem_size() const = 0; // >>>> SM will implement this while instantialize HomeObject.
...
}

void HSHomeObject::init_homestore() {
...
    const uint64_t app_mem_size = app->app_mem_size();
...
}

Slack Discussion.
https://ebay-eng.slack.com/archives/CAVQXEAKS/p1739472960517899