Add support for hybrid-array

[Lohann]

Related PR: #204

I'm migrating a no_std project from generic-array to hybrid-array, and to get tinyvec::ArrayVec working again I must implement tinyvec::Array for hybrid_array::Array struct, which uses ArraySize for define the array length.

So this PR does:

• Adds hybrid-array 0.4 as an optional dependency.
• Bump generic-array 1.1.1 to 1.4.1.
• implements the trait tinyvec::Array for hybrid_array::Array struct. when hybrid-array is enabled.
• implements the trait generic_array::IntoArrayLength for tinyvec::ArrayVec when generic-array is enabled.
• implements the trait hybrid_array::AssocArraySize for tinyvec::ArrayVec when hybrid-array is enabled.
• Enable hybrid-array/arbitray and generic-array/arbitrary when arbitrary is enabled.
• Enable hybrid-array/serde and generic-array/serde when serde is enabled.

[Lokathor]

I'm not keen on a 0.4 dependency. Is there any timeline for when they'd be moving to a 1.0 version?