Add a new Sizeable interface in cadence common cache

[timl3136]

What changed?
Add a new Sizeable interface that implements Size() function which returns the size of that interface in bytes

Why?
We want to modernize existing cadence common cache implement to a bytes-based system. That means we need to have a method to measure each entry (which is currently accepting any generic interface). We found the "Reflect" package provides a measuring function but runtime is too slow to be used in cache operations. Therefore, we will require all usages to implement the Size() function in their cache logic if they want to migrate to the new bytes-based system.

In order to seamless transition from the current cache system with an entry-based model, the implementation and rollout will be done in following phases:

1. Define the Sizeable interface <-- This PR
2. Implement Sizeable for cadence-history service
   a. Implement Size() for ExecutionCache
   b. Implement Size() for EventCache
3. Implement bytes-based cache system
4. Enable new cache system for usage in cadence-history service
5. Implement and enable new cache system for the remaining usages

How did you test it?
This is only an addition of a new interface that is not used.

Potential risks
No risk since it's only an addition of a new interface that is not used.

Release notes

Documentation Changes

[3vilhamster]

Size() int is already provided by cache.Cache and is supplied by lru type.
Maybe we can use a different name? Or change the existing Size to Len? I think having two different functions for Size can be confusing.

[taylanisikdemir]

Size() int is already provided by cache.Cache and is supplied by lru type. Maybe we can use a different name? Or change the existing Size to Len? I think having two different functions for Size can be confusing.

This is for size of the entries