Pagination support for listing workflows through a new Client#list_workflow_page method

[jeromepl]

Thought this was a straightforward enough change, but I am happy to also open an issue if more discussions are needed.

What was changed

Added support for getting a list of workflows one page at a time in a new method Client#list_workflow_page. Example:

first_page = client.list_workflow_page(query, page_size: 10)
first_page.executions.each do
  # ...
end

second_page = client.list_workflow_page(query, page_size: 10, next_page_token: first_page.next_page_token)

Why?

Fetching all workflow executions matching a query can be extremely expensive if there are a lot of matches. The risk of hitting rate limit or other RPC errors is high, and a lot of the time getting all the results is not necessary.
For example, in a user interface showing a list of workflows one page at a time, we want to only get the list of workflows for the currently shown page.

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[cretz]

Thanks! Mentioned in comment, let's think on design of this just a bit. I opened an issue to track the work.

[jeromepl]

@cretz ready for a new round of review after going with the new approach discussed in #288

[cretz]

Thanks! Only a few hopefully-minor things.

[cretz]

It looks like there may be CI failures for two things not related to this issue (generated protos have a bit of a new format it seems and Rubocop just released a new check). This is kinda our fault for not using a lock file and always running CI, intentionally, against latest versions. I will fix in #291 before I merge it and then will merge main here (and #286).

[cretz]

Looks great! Thanks for sticking with this. Only minor change is to remove < Data. I am working on getting CI fixed in another PR.

[cretz]

Thanks! Will be merging #291 (fixes CI), then #286, then this.