feat(templates): add prefix and suffix string template functions

[rubenhoenle]

Related Issue

relates to #591

Description

Registered the default strings.HasPrefix and strings.HasSuffix string functions for usage in the templates.

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

[hashicorp-cla-app]

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[hashicorp-cla-app]

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