Fix account deletion blocked by deleted project admin mappings

[SURYAS1306]

Description

When attempting to delete an account, CloudStack currently blocks the deletion if the
account is listed as an administrator of any project, even when those projects have
already been deleted (i.e. removed is not null).

This leads to a misleading error and prevents valid account deletion for accounts that
only manage already-deleted projects.

This PR improves the account deletion flow by ensuring that only active projects
are considered when checking whether an account manages projects. Deleted projects are
ignored, allowing the account deletion to proceed correctly.

A unit test has been added to validate this behavior and prevent regressions.

Fixes #12601

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Expected behavior

An account should be deletable if it only manages projects that have already been deleted.

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Actual behavior

Account deletion fails with an error indicating that the account manages projects,
even when all associated projects are already deleted.

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Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Test (unit test code)

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Bug Severity

• Minor

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How Has This Been Tested?

• Added a unit test in AccountManagerImplTest to verify that an account managing
  only deleted projects does not cause account deletion to fail.
• Verified that the account deletion logic continues to block deletion when the
  account manages active projects.
• Built the affected CloudStack modules locally using Maven.

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How did you try to break this feature and the system with this change?

• Simulated scenarios where an account manages:
  • only deleted projects
  • a mix of active and deleted projects
• Confirmed that deletion is allowed only when no active projects are managed,
  and correctly blocked otherwise.