Add support to the Runtime Defined Entities (RDE) framework with RDE types (2/3)

[adambarreiro]

Overview

This PR is built on top of #527, review and merge that one first.

This PR implements the foundations to onboard the RDE framework to the Terraform VCD Provider, by adding CRUD capabilities of RDE types.

Detailed description

This PR adds the following features:

• Adds the following new methods to the generic VCDClient:
  • CreateRdeType to create a RDE type.
  • GetAllRdeTypes to get all RDE types, supports parameters like filtering.
  • GetRdeType gets a RDE types with its vendor+namespace+version combination which is unique.
  • GetRdeTypeById gets a RDE type with its URN, which is a combination of its vendor+namespace+version underneath.
• Adds the following methods to the new DefinedEntityType type:
  • Update updates a RDE type with the given input. It is a bit smart to avoid errors if Name and Schema are not populated for update (ie: User doesn't want to update them, but they're mandatory).
  • Delete deletes a RDE type. The RDE type can't be deleted if it's referenced by some RDE instances.

[Didainius]

Looks good, tests passed on 10.4.0 and 10.4.1.