ed25519 ssh key support for compute and storage account local user

[gerrytan]

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Description

Adds support for ed25519 ssh key for compute resource (already supported in az cli) and storage account local user resource.

PR Checklist

• I have followed the guidelines in our Contributing Documentation.
• I have checked to ensure there aren't other open Pull Requests for the same update/change.
• I have checked if my changes close any open issues. If so please include appropriate closing keywords below.
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  For example: “resource_name_here - description of change e.g. adding property new_property_name_here”

Changes to existing Resource / Data Source

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Testing

• My submission includes Test coverage as described in the Contribution Guide and the tests pass. (if this is not possible for any reason, please include details of why you did or could not add test coverage)

• Manual testing: can deploy a linux vm with ed25519 ssh key, and connect to it via bastion - main.tf - terraform apply log ✅
• make acctests SERVICE='compute' TESTARGS='-run=TestAccLinuxVirtualMachine_auth' TESTTIMEOUT='120m' - output log ✅
• make acctests SERVICE='compute' TESTARGS='-run=TestAccOrchestratedVirtualMachineScaleSet_' TESTTIMEOUT='120m' - output log ✅ (there are race condition errors on resource cleanup but unrelated to this change)
• make acctests SERVICE='storage' TESTARGS='-run=TestAccLocalUser_' TESTTIMEOUT='120m' - output log ✅

Change Log

Below please provide what should go into the changelog (if anything) conforming to the Changelog Format documented here.

• azurerm_linux_virtual_machine, azurerm_storage_account_local_user - adds support for ed25519 ssh key [provider does not support ed25519 ssh keys while azure does. #26587]

This is a (please select all that apply):

• Bug Fix
• New Feature (ie adding a service, resource, or data source)
• Enhancement
• Breaking Change

Related Issue(s)

#26587

Note

If this PR changes meaningfully during the course of review please update the title and description as required.

[magodo]

Thanks for this PR!
I've taken a look through and left some comments inline, but this is mostly looking good to me 👍

[catriona-m]

Thanks @gerrytan LGTM!

[github-actions]

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