Add accelerators workstation config resource

[DanielRieske]

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Generated Terraform providers, and ran make test and make lint in the generated providers to ensure it passes unit and linter tests.
• Ran relevant acceptance tests using my own Google Cloud project and credentials (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read Write release notes before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

workstations: added `accelerators` field to `google_workstations_workstation_config` resource(beta)

Closes: hashicorp/terraform-provider-google#15311

[DanielRieske]

Note: I was not able to run all acceptances tests at the same time as my project had a quota of 5 on the amount of clusters that I could create within my region. I assume that the project that this is tested in has a higher quota otherwise I'll have to revist the tests.

WorkstationClustersPerProjectPerRegion' exhausted. Limit 5 in region us-central1

[modular-magician]

Oops! It looks like no changelog entry is attached to this PR. Please include a release note block in the PR body, as described in https://github.com/GoogleCloudPlatform/magic-modules/blob/master/.ci/RELEASE_NOTES_GUIDE.md:

```release-note:TYPE
Release note
```

[modular-magician]

Hello! I am a robot. It looks like you are a community contributor. @rileykarson, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 73 insertions(+))
Terraform Beta: Diff ( 3 files changed, 256 insertions(+))
TF Conversion: Diff ( 3 files changed, 47 insertions(+), 3 deletions(-))
TF OiCS: Diff ( 4 files changed, 149 insertions(+))

[modular-magician]

Tests analytics

Total tests: 2911
Passed tests 2607
Skipped tests: 302
Affected tests: 2

Action taken

Found 2 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccContainerAwsNodePool_BetaBasicHandWritten|TestAccWorkstationsWorkstationConfig_workstationConfigAcceleratorsExample

Get to know how VCR tests work

[modular-magician]

$\textcolor{green}{\textsf{Tests passed during RECORDING mode:}}$
TestAccWorkstationsWorkstationConfig_workstationConfigAcceleratorsExample[Debug log]

Rerun these tests in REPLAYING mode to catch issues

$\textcolor{green}{\textsf{No issues found for passed tests after REPLAYING rerun.}}$

---

$\textcolor{red}{\textsf{Tests failed during RECORDING mode:}}$
TestAccContainerAwsNodePool_BetaBasicHandWritten[Error message] [Debug log]

$\textcolor{red}{\textsf{Please fix these to complete your PR.}}$
View the build log or the debug log for each test

[modular-magician]

Oops! It looks like no changelog entry is attached to this PR. Please include a release note block in the PR body, as described in https://github.com/GoogleCloudPlatform/magic-modules/blob/master/.ci/RELEASE_NOTES_GUIDE.md:

```release-note:TYPE
Release note
```

[DanielRieske]

Unsure why my changelog entry isn't going through the validator.

release-note:enhancement
workstations: added `accelerators` field to `google_workstations_workstation_config` resource(beta)

[rileykarson]

Ah, there was a space between the ``` and release-note. Fixed it.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 73 insertions(+))
Terraform Beta: Diff ( 3 files changed, 256 insertions(+))
TF Conversion: Diff ( 3 files changed, 47 insertions(+), 3 deletions(-))
TF OiCS: Diff ( 4 files changed, 149 insertions(+))

[modular-magician]

Tests analytics

Total tests: 2912
Passed tests 2609
Skipped tests: 302
Affected tests: 1

Action taken

Found 1 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccContainerAwsNodePool_BetaBasicHandWritten

Get to know how VCR tests work

[modular-magician]

$\textcolor{red}{\textsf{Tests failed during RECORDING mode:}}$
TestAccContainerAwsNodePool_BetaBasicHandWritten[Error message] [Debug log]

$\textcolor{red}{\textsf{Please fix these to complete your PR.}}$
View the build log or the debug log for each test