feature: improve memory allocation for marshall go map type

[dinhxuanvu]

Is your feature request related to a problem? Please describe.
Marshalling go map type to CBOR is a common operation that can be expensive memory-wise of the map has a lot of fields. The code in CBOR uses map iteration that will allocate memory for each field and value. This excessive memory allocation is described in this issue on golang [1].

Describe the solution you'd like
Starting with go 1.18, there are two new methods Value.SetIterKey and Value.SetIterValue that will do fewer allocations.

Plus, the sync.Pool is also another tool that can be used to further reduce memory allocation by reusing temporary memory allocation.

Lastly, the Value.SetZero method (available since go 1.20) is helpful to release memory allocation to the GC when is no longer needed.

Additional context
The new methods SetIterKey and SetIterValue are introduced in go 1.18 and unavailable for go 1.17 or before while SetZero is available starting go 1.20. In order to maintain the backward compatibility for the CBOR codebase (if this is a concern), the code for encode map can be refractored into separate files where a go:build tag can be used to specify which files can be included in compilation for go 1.18+/1.20+ and what not.

The performance/memory improvement can be seen here (collected and analyzed by go benchmark and benchstat):

[dinhxuanvu]

This feature has been completed.
/close