In addition to thread_local -> lazy_static change, a number of thread-pools are
initialized with get_max_thread_count to achieve parity with the older code in
terms of number of validator threads.
The extra wrapping and indirection by the Session struct is not used in
any form. The commit removes Session and instead uses Reed-Solomon
constructs directly.
Removed Default implementation for ShredType. ShredType should always be
explicitly specified, and not rely on default values.
Simplified single-arg Shred Error variants to use shorter syntax.
Renamed erasure blocks to shards, to be consistent with reed_solomon
crate and not to confuse with FEC blocks.
behzad nouri