[BUG] Unable to Set Nested agents variable values from Toolkit Side in Agents or Pipelines

[SamvelSimonyan]

Precondition
An agent exists with a variable

Steps to reproduce:

1. Create an agent/pipeline and add a nested agent with a variable
2. Attempt to override the variable value

Actual results:
-No variable field is created with the "agent" node type

• There is no available mechanism to set/override the value of the nested agent's variable from the parent agent/ node side.

https://epam-my.sharepoint.com/:v:/p/samvel_simonyan/EYVm4nW1adBLv5pWb4jZJBIBYzt4_2Mx21hivT-kz1MlYg?nav=eyJyZWZlcnJhbEluZm8iOnsicmVmZXJyYWxBcHAiOiJPbmVEcml2ZUZvckJ1c2luZXNzIiwicmVmZXJyYWxBcHBQbGF0Zm9ybSI6IldlYiIsInJlZmVycmFsTW9kZSI6InZpZXciLCJyZWZlcnJhbFZpZXciOiJNeUZpbGVzTGlua0NvcHkifX0&e=5QRcGp

Expected results:

• Users should be able to set/override the value of the nested agent's variables from the toolkit side.
  E.g. from nexus

[epamLDadayan]

@SamvelSimonyan please check on NEXT env as a part of Agent node now.