Gitlab key management for execution nodes

[prasadtalasila]

Description

With the execution nodes installed on multiple computers, it becomes difficult to keep track of the keys that are in use vs keys that are no longer needed.

We need a way to manage the keys of execution nodes in GitLab. The following situations need explicit key management.

1. Conflict resolution during addition.
   If by mistake two execution nodes added on two servers have the same name, there is going to be a conflict at GitLab level. We need to uniquely construct the key names from the unique name strings of execution nodes.

2. Removal of a key during uninstallation.
   When one or more execution nodes are being removed from a server, the corresponding keys must also be removed from GitLab.