fix: fieldarray deserialization fail

[jdelgadoalfonso]

Fieldarray deserialization fail because of length counts bytes instead of number of elements in the array.

Making an app which consumes from a queue that is bind to the RabbitMQ event exchange plugin, I faced up with a panic deserializing the header.

There is a client_properties field of type FieldArray. RabbitMQ is filling the length with the number of bytes instead of the number of elements of the given array

[gftea]

Thanks very much for your PR!

[codecov]

Codecov Report

Merging #64 (cb14008) into main (cc5dfda) will decrease coverage by 0.21%.
The diff coverage is 76.78%.

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
- Coverage   85.33%   85.12%   -0.21%     
==========================================
  Files          42       42              
  Lines        5850     5931      +81     
==========================================
+ Hits         4992     5049      +57     
- Misses        858      882      +24     

Impacted Files	Coverage Δ
amqp_serde/src/ser.rs	82.26% <35.71%> (-4.29%)	⬇️
amqp_serde/src/types.rs	72.80% <52.77%> (-0.98%)	⬇️
amqp_serde/src/de.rs	92.51% <100.00%> (+0.81%)	⬆️
amqprs/src/api/connection.rs	87.19% <0.00%> (-0.45%)	⬇️
amqprs/src/frame/mod.rs	84.78% <0.00%> (+1.08%)	⬆️
amqprs/src/api/error.rs	44.44% <0.00%> (+11.11%)	⬆️

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