Swap RPC & Txn version

[Gauthamastro]

Describe your changes

1. RPC to access swap state
2. Decrement txn version as a hot fix for ledger users.

[codecov]

Codecov Report

Attention: 25 lines in your changes are missing coverage. Please review.

Comparison is base (390523c) 37.49% compared to head (5f0f730) 37.25%.
Report is 7 commits behind head on mainnet-release.

Files	Patch %	Lines
rpc/swap/src/lib.rs	0.00%	22 Missing ⚠️
pallets/ocex/src/validator.rs	0.00%	2 Missing ⚠️
nodes/mainnet/src/node_rpc.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##           mainnet-release     #891      +/-   ##
===================================================
- Coverage            37.49%   37.25%   -0.24%     
===================================================
  Files                   62       63       +1     
  Lines                 3753     3777      +24     
===================================================
  Hits                  1407     1407              
- Misses                2346     2370      +24     

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