feat: [CON-1567] add some load metrics to `CanisterMetrics` in the `ReplicatedState`

[kpop-dfinity]

These metrics could be later used to determine how to split a subnet, if necessary.

Metrics tracked per canister

1. Number of ingress messages executed (8 bytes)
2. Number of xnet requests/responses executed (8 bytes)
3. Number of intranet requests/responses executed (8 bytes)
4. Number of http outcalls executed (8 bytes)
5. Total number of instructions executed (8 bytes)

Note: In total they increase the size of the replicated state by 40 bytes per canister.

Next steps

In a subsequent PR (https://github.com/dfinity/ic/pull/8082) we will be adding tools to read these metrics