Support pagination for entity query

[inespo]

Entity service needs to support pagination for querying entities.

The use case for this is: UI implementation that needs pagination on large set of entities.

An option is implements orderBy, offset and limit. However, as @jcchavezs has mentioned offset and limit has accuracy issue if not support by snapshot view. For example,
t = 0, Client fetches entities with offset 0, limit 5
t = 1, entity is added and by the specified order, it's at index 4.
t = 2, Client fetches next batch with offset 5, limit 5. --> Client will miss the newly added entity or potentially processing an entity twice if an entity was deleted.

Several alternatives that were discussed:

1. Leverages the underlying data storage cursor management and exposes an iterator
2. Snapshot view / replica view to use pagination with

[inespo]

While orderBy, offset, and limit won't be completely accurate when there's entity mutation, it does however will help to process data at larger scale and with pagination.

So, this is a solution with limitation, and we need to expand it to have Snapshot View support in the future.

[kotharironak]

is it done?
cc: @rish691