add govcloud support

[onchrs]

Description

This change adds us-gov-west-1 as a valid region for cli support.

Related Issue

Closes #

Documentation PR

None required

Type of Change

• [ X] Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

How have you tested the change?

• [ X] I ran npm run test:unit and npm run test:integ
• [ X] I ran npm run typecheck
• [ X] I ran npm run lint
• If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Checklist

• [ X] I have read the CONTRIBUTING document
• [ X] I have added any necessary tests that prove my fix is effective or my feature works
• [ NA] I have updated the documentation accordingly
• [ X] I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• [X ] My changes generate no new warnings
• [ NO ] Any dependent changes have been merged and published. This change requires a change to agentcore-cdk. This change can be merged without the cdk change but agent creation and deployment will not work.

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