FEAT: Encode expected/actual info in ShapeError

Add a (limited) way to add specific information to a ShapeError

Admittedly wonky, but space efficient.

Result<(), ShapeError> used to be 1 byte, and with this change it
expands to 16 bytes (2 usize on 64-bit).

The remaining 15 bytes are used for optimistically packing as much of
extra info into the error message as possible.

For example we can store expected/actual index for errors (for example
index out of bounds or axis out of bounds, these are not so commonly
handled with ShapeError).

With this change it is supported:

- Expected/actual index with 7 bytes per index
- Expected/actual shape with 7 bytes per shape
  supports storing shapes with one or two bytes (< 256²) per dimension,
  with limited ndim.

Author: bluss

Cargo.toml

@@ -49,6 +49,7 @@ defmac = "0.2"
 quickcheck = { version = "0.9", default-features = false }
 approx = "0.4"
 itertools = { version = "0.10.0", default-features = false, features = ["use_std"] }
+matches = "0.1.8"
 
 [features]
 default = ["std"]