[CDTOOL-1265] Move vcl commands under service

[rcaril]

Change summary

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

• Does your submission pass tests?

// Sampled a few tests, they all seems to run
make test TEST_ARGS="-run TestConditionCreate ./pkg/commands/service/vcl/condition"
ok      github.com/fastly/cli/pkg/commands/service/vcl/condition        1.050s
make test TEST_ARGS="-run TestCustomCreate ./pkg/commands/service/vcl/custom"
ok      github.com/fastly/cli/pkg/commands/service/vcl/custom   1.024s [no tests to run]
make test TEST_ARGS="-run TestSnippetCreate ./pkg/commands/service/vcl/snippet"
ok      github.com/fastly/cli/pkg/commands/service/vcl/snippet  1.022s [no tests to run]
make test TEST_ARGS="-run TestVCLDescribe ./pkg/commands/service/vcl"
ok      github.com/fastly/cli/pkg/commands/service/vcl  1.063s

Changes to Core Features:

• Have you written new tests for your core changes, as applicable?
• Have you successfully run tests with your changes locally?

User Impact

Anyone using the fastly vcl and / or sub-commands will need to adjust for the vcl commands now being under the service bucket.

Are there any considerations that need to be addressed for release?

See above.

[rcaril]

Wasn't too sure on the naming convention here. Open to discuss how we should refer to this nested top level command.

[rcaril]

I realized the alias work still needs to be done, so moving this back to draft.