ec_deployment: Add support for deployment aliases

[marclop]

Description

Adds support for deployment aliases on both the ec_deployment resource
and ec_deployment datasource.

Related Issues

Closes #287

How Has This Been Tested?

Manual, unit and acceptance tested.

Types of Changes

• New feature (non-breaking change which adds functionality)

[alaudazzi]

LGTM for the .md files

[karencfv]

🏅

[marclop]

TestAccDeployment_basic_config seems to return with a non-empty plan on step 2/3:

12:11:27  === CONT  TestAccDeployment_basic_config
12:11:27      deployment_basic_test.go:95: Step 2/3 error: After applying this test step, the plan was not empty.
12:11:27          stdout:
12:11:27          
12:11:27          
12:11:27          Terraform used the selected providers to generate the following execution
12:11:27          plan. Resource actions are indicated with the following symbols:
12:11:27            ~ update in-place
12:11:27          
12:11:27          Terraform will perform the following actions:
12:11:27          
12:11:27            # ec_deployment.basic will be updated in-place
12:11:27            ~ resource "ec_deployment" "basic" {
12:11:27                ~ alias                  = "terraform-acc-tnvcsx8mmv" -> "basic"
12:11:27                  id                     = "36f2ce73ef9c96b8f5c943a451098043"
12:11:27                  name                   = "terraform_acc_tnvcsx8mmv"
12:11:27                  tags                   = {}
12:11:27                  # (6 unchanged attributes hidden)
12:11:27          
12:11:27          
12:11:27          
12:11:27          
12:11:27                  # (4 unchanged blocks hidden)
12:11:27              }
12:11:27          
12:11:27          Plan: 0 to add, 1 to change, 0 to destroy.

I'll take a look.

[marclop]

Tests look alright, I think we can merge this. @karencfv