asim: update node capacity in updateStoreCapacity

[wenyihu6]

This commit updates node capacity directly in updateStoreCapacity, which is called by StoreDescriptors - the component responsible for updating store capacity. This removes the need to populate the node capacity field before gossip and aligns the simulator more closely with the production code. Note that we update node capacity regardless of the useCached flag since this is also what the production code does.

Epic: none
Release note: none

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is