[Enhance] - `azuredevops_build_definition` - Add support for `build_completion_trigger`

[xuzhang3]

All Submissions:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] My code follows the code style of this project.
• [x] I ran lint checks locally prior to submission.
• [x] Have you checked to ensure there aren't other open PRs for the same update/change?

What about the current behavior has changed?

close: #1192

Does this introduce a change to go.mod, go.sum or vendor/?

• [ ] Yes
• [x] No

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Any relevant logs, error output, etc?

(If it’s long, please paste to https://ghostbin.com/ and insert the link here.)

Other information

[xuzhang3]

=== RUN   TestAccBuildDefinition_DataSource
=== PAUSE TestAccBuildDefinition_DataSource
=== RUN   TestAccBuildDefinition_with_path_DataSource
=== PAUSE TestAccBuildDefinition_with_path_DataSource
=== RUN   TestAccBuildDefinition_basic
=== PAUSE TestAccBuildDefinition_basic
=== RUN   TestAccBuildDefinition_pathUpdate
=== PAUSE TestAccBuildDefinition_pathUpdate
=== RUN   TestAccBuildDefinition_withVariables
=== PAUSE TestAccBuildDefinition_withVariables
=== RUN   TestAccBuildDefinition_schedules
=== PAUSE TestAccBuildDefinition_schedules
=== RUN   TestAccBuildDefinition_buildCompletionTrigger
=== PAUSE TestAccBuildDefinition_buildCompletionTrigger
=== CONT  TestAccBuildDefinition_DataSource
=== CONT  TestAccBuildDefinition_withVariables
=== CONT  TestAccBuildDefinition_pathUpdate
=== CONT  TestAccBuildDefinition_basic
=== CONT  TestAccBuildDefinition_with_path_DataSource
=== CONT  TestAccBuildDefinition_buildCompletionTrigger
=== CONT  TestAccBuildDefinition_schedules
--- PASS: TestAccBuildDefinition_with_path_DataSource (237.15s)
--- PASS: TestAccBuildDefinition_schedules (259.10s)
--- PASS: TestAccBuildDefinition_basic (325.45s)
--- PASS: TestAccBuildDefinition_DataSource (326.38s)
--- PASS: TestAccBuildDefinition_buildCompletionTrigger (332.00s)
--- PASS: TestAccBuildDefinition_pathUpdate (393.73s)
--- PASS: TestAccBuildDefinition_withVariables (397.82s)
PASS
ok      github.com/microsoft/terraform-provider-azuredevops/azuredevops/internal/acceptancetests        398.516s