Destructible v7.0.0-alpha.0

• Indicate desire to raise exception with boolean. Closes #189.
• Do not include cause on ephemeral error. Closes #188.
• Use linked list instead of array. Closes #187.
• Remove the rest of attemptable. See #184.
• Benchmark overhead. Closes #186.
• Raise exception on new strand when destroyed. Closes #185.
• Remove attemptable. Closes #184.
• Remove sub-destructible specific timeout.
• Return value directly from strand launch. Closes #183.
• Shutdown progress, ephemerals inherit scram.

Closes #190.