Added a new rpc call workflow.GetWorkflowContextList to be used by boots

[gauravgahlot]

Description

As the worker starts, Boots checks if there is a workflow defined for that worker. If yes, it will continue to PXE and it will not otherwise. (more context here).

The PR introduces a new RPC that can be used by Boots to get the workflow contexts without having to maintain a gRPC stream.

Why is this needed

Recently there have been changes in Tink, to allow a worker to maintain a gRPC stream with the server to get the workflows. The same RPC was being by boots.

How Has This Been Tested?

Still a WIP.

How are existing users impacted? What migration steps/scripts do we need?

No direct impact on users.

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• added unit or e2e tests
• provided instructions on how to upgrade

[Cbkhare]

Let me first test it with boots then merge it.

[Cbkhare]

changes done in accordance with #238

[gianarb]

Can we write a unit test for this?! I would like to have a table test that insert a set of fixtures and checks what we expect. This is a crucial part of the application @gauravgahlot can you add that to this PR?

[Cbkhare]

Tested the workflow execution using this PR. changes are working correctly.
For more ref follow tinkerbell/smee#64

[Cbkhare]

Can we write a unit test for this?! I would like to have a table test that insert a set of fixtures and checks what we expect. This is a crucial part of the application @gauravgahlot can you add that to this PR?

@gianarb Will it be fine if we merge this PR and @gauravgahlot can add table test for it in a separate PR. To fix issues related to #222 , this is a kind of priority.

[gianarb]

Yes I agree but let's get it done as soon as it is merged please

[Cbkhare]

Yes I agree but let's get it done as soon as it is merged please

Thanks @gianarb ,