Backport of Add Enigma Vault secret plugin to community plugin list into release/1.10.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #14389 to be assessed for backporting due to the inclusion of the label backport/1.10.x.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

The below text is copied from the body of the original PR.

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Designed to be simple but complete, this Enigma machine as a Vault plugin is a good starting point for plugin developers, including:

1. The build environment
2. Code organization
3. Your first function
4. Debugging
5. Unit testing
6. Accepting parameters
7. Different paths for different purposes
8. Persist state and secrets
9. Upgrading your plugin

[hashicorp-cla]

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2 out of 3 committers have signed the CLA.

• ixe013
• ncabatoff
• temp

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[hghaf099]

Seems like the cherry-pick failed?