1.8.0 Release

New features/interfaces:

• Add Message binary decoding support from ContiguousBytes (#914)
• Make things generic over ContiguousBytes and @inlinable (#915, #921)

Notable changes:

• Use heap-based storage only when a Protobuf has a singular transitive recursion (#900)
• Use raw pointers instead of typed pointers (#918)
• Add missing CaseIterable support for nested enums (#923)
• Guard against TextFormat encoding of unknowns from overflowing the stack (#927)

Performance related changes:

• JSON/TextFormat submessage encoding performance improvements (#916)
• Avoid collecting unknown fields while scanning for message (#924)
• Minor code cleanup for JSON additions (#935)