Add trigger patterns and working directory fields to Stack options

[aaabdelgany]

Description

This PR adds support for the newly released Stacks trigger patterns and working directory fields.

Testing plan

1. Create a stack and specify a working directory or trigger pattern upon creation
2. Trigger a stacks config via a modification to a path under the trigger pattern. Alternatively, fetch a new config and make sure that your configuration code lives under the working directory you specified.
3. observe that the config processes successfully
4. Modify the working directory and trigger patterns as you like and test with subsequent configs

External links

Output from tests

go test -v -run TestStackReadUpdateDelete
=== RUN   TestStackReadUpdateDelete
=== PAUSE TestStackReadUpdateDelete
=== CONT  TestStackReadUpdateDelete
--- PASS: TestStackReadUpdateDelete (5.52s)
PASS
ok  	github.com/hashicorp/go-tfe	6.018s

Rollback Plan

Changes to Security Controls

[arunatibm]

Should this be an enhancement? OK really either way.

[datadog-terraform-cloud-hashicorp]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

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