Skips gap fields in struct and arrays.
Gaps fields are bit ranges that a decoder did not add any fields for.
Note that skipping gaps in arrays will affect indexes.
Preparation to make decoder use less memory and API more type safe.
Now each scalar type has it's own struct type so it can store different
things and enables to have a scalar interface.
Also own types will enable experimenting with decode DLS designs like
using chained methods that are type aware.
Rework time helpers to use new functions
Fix panic in tar decoder where sym value might be missing
Still not very happy about the API but it's getting better.
Was already handled in fq in various places as gojq uses them
Update msgpack to support negative integers that can't represented as int64
Rename read try* number functions to make them more explicit
Move scalar into own package.
Split scalar code into decode related scalar code (that reads etc) and
scalar code that just transform the scalar value.
Use a scalar.Mapper interface instead of just a function.
Make mappers, assert and validat impement the interface.
