Payload decoding update

[prd-fox]

When decoding a payload that has no recipients, return an empty list without further inspection of the byte buffer.

This reduces the need to calling methods to determine ahead of time
which of the decode methods should be called.

[codecov-io]

Codecov Report

Merging #501 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #501      +/-   ##
============================================
+ Coverage     99.38%   99.38%   +<.01%     
- Complexity     1260     1261       +1     
============================================
  Files           217      217              
  Lines          4070     4072       +2     
  Branches        213      214       +1     
============================================
+ Hits           4045     4047       +2     
  Misses            5        5              
  Partials         20       20

Impacted Files	Coverage Δ	Complexity Δ
...quorum/tessera/transaction/PayloadEncoderImpl.java	98.93% <100%> (+0.02%)	11 <0> (+1)	⬆️

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