Add Zero AccountSetFlag

[nkramer44]

Ledger 39597277 on testnet contains an AccountSet transaction where ClearFlag is 0. AccountSetFlag does not have an enum value for 0, so the AccountSet transaction failed to get deserialized to an AccountSet xrpl4j object. This PR adds a new AccountSetFlag called NONE that maps to 0.

[codecov]

Codecov Report

Merging #459 (591d082) into main (7823236) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main     #459   +/-   ##
=========================================
  Coverage     90.43%   90.44%           
  Complexity     1464     1464           
=========================================
  Files           285      285           
  Lines          4163     4164    +1     
  Branches        339      339           
=========================================
+ Hits           3765     3766    +1     
  Misses          277      277           
  Partials        121      121           

Impacted Files	Coverage Δ
...org/xrpl/xrpl4j/model/transactions/AccountSet.java	95.45% <100.00%> (+0.10%)	⬆️