Allow encoding/decoding of HashMap and HashSet with custom hash algorithms

[bronsonp]

The current implementations of Encode and Decode for HashMap and HashSet are only defined for the default hash algorithm. However, these types also allow a custom hash type to be defined. At present, maps and sets using custom hashers cannot be handled by bincode.

This pull request adds the necessary functionality to support custom hash algorithms. The main change is the use of with_capacity_and_hasher instead of with_capacity when creating the new object in the Decode implementation.

The pull request also adds test cases in tests/std.rs to ensure that both HashMap and HashSet with custom hash algorithms can be handled successfully.

[codecov]

Codecov Report

Merging #529 (ba290c5) into trunk (650fa39) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            trunk     #529      +/-   ##
==========================================
+ Coverage   71.02%   71.16%   +0.14%     
==========================================
  Files          47       47              
  Lines        3182     3198      +16     
==========================================
+ Hits         2260     2276      +16     
  Misses        922      922              

Impacted Files	Coverage Δ
src/features/impl_std.rs	79.88% <100.00%> (+0.24%)	⬆️
tests/std.rs	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 650fa39...ba290c5. Read the comment docs.

[VictorKoenders]

Looks good to me, thanks! 👍