Review Mojo's priorities

• I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

See parent issue

The following kernel files should be migrated off of LegacyUnsafePointer. (complexity noted next to file)

extensibility/tensor/managed_tensor_slice.mojo (High)
internal_utils/_measure.mojo (Medium)
internal_utils/_testing.mojo (Medium)
internal_utils/_utils.mojo (Medium)
kv_cache/types.mojo (Medium)

What is your motivation for this change?

LegacyUnsafePointer is being deprecated and removed.

Any other details?

No response