Update language in experimental RPC API paramaters

[mattias-p]

Purpose

This PR updates the terminology used in experimental RPC API methods.

• Use "job id" instead of "test id", "hash id" or just "id".
• Avoid using to "frontend".
• Abbreviate cardinal "number" as "num" instead of "nb". Is "nb" a french abbreviation? It feels foreign to me. (I also considered using "no" as in №, but that's for ordinal numbers and these are cardinal numbers.)

Context

Fixes #1084.

Changes

In the RPC API the following input and output parameters are renamed.

RPC method	Parameter type	Old parameter name	New parameter name
job_status	input	test_id	job_id
job_params	input	test_id	job_id
job_results	input	id	job_id
job_results	output	hash_id	job_id
domain_history	input	frontend_params	params
domain_history	output	history[].id	history[].job_id
batch_create	input	test_params	job_params
batch_status	output	finished_test_ids	finished_job_ids
batch_status	output	nb_finished	finished_count
batch_status	output	nb_running	running_count

How to test this PR

Make calls to each RPC method in the table above and make sure it accepts the new input parameters and that the new output parameters are present in the output.

[marc-vanderwal]

Yes, “nb” is a usual French shorthand for “nombre”. So variable names such as nb_running are technically what we call franglais. I agree that “nb” ought to be replaced with “num” or something to that effect.

[hannaeko]

May I suggest finished_count and running_count instead of num_finished and num_running, to get rid of the abbreviated num altogether?

[mattias-p]

Sure, I like it. I'll make an update.