Include load_balancer in configuration unit tests

LoadBalancerService added to initial 'all configurations are changed' test.

More cases to be come...
Add load balancer to 'nothing changed' config test

'all configs are present but haven't changed' now includes LoadBalancer
DRY out edge_gateway_configuration test
fix indentation
Specific load_balancer-only update test
Update existing tests to include load_balancer in context
Add load_balancer-only test
Add "two things have changed" test

... to ensure logic is ok in not-1, not-all case
Remove use of and_call_original

As per NatService specific tests, remove need to have rSpec and_call_original
call in the test path - this is risky in an integration test.

This also aligns the method that we are using to test how many times the
edgeGateway has been updated, so is ripe for DRYing out.
Version bump and CHANGELOG update
Add test to ensure nat_rules order is preserved
Fix mock data in EdgeGatewayConfiguration test

The test double of Core::EdgeGateway.vcloud_gateway_interface_by_id
is hardcoded to return a particular Interface section.

Make the inputs for tests match this double, otherwise the tests don't
really make sense.

This limitation with the mocking is addressed when we move to dependency
injection for the generators.
Add load balancer to test context

Missed one of the tests when adding the LoadBalancerService
Further clarification of different test data

... for LoadBalancerService
Add tests for 'no remote config' case; fix bug

These tests assume the case where there is a missing remote
configuration for a given service, for which we are subsequently
trying to configure.

Highlighted a NilClass exception in LoadBalancerConfigurationDiffer,
which is fixed in this commit.
Add test that missing remote service is ok

Specifically, test that we can update the NatService when we
there is no remote LoadBalancerService specified.
Merge pull request #7 from alphagov/load_balancer_general_case_tests

[#64583056] Load balancer general case tests
Remove magic number for NatService Id
Remove test_cases array, use regular tests instead.

The test_cases iteration was a trial, and its usefulness
was very limited. Update tests so that they are individual
it 'blah' do .. end blocks
Replace use of constand for BASE_NAT_ID

... with a regular rspec instance variable.

The use of the constant was a hack required by the test_cases
array, refactored out in the previous commit.