refactor(x/ecocredit): consistent origin tx and separate mint events

[ryanchristo]

Description

This pull request make the following changes:

• renames the state message BatchOrigTx to BatchOriginTx
• updates OriginTx and BatchOriginTx field name typ to source (consistent with outbound target)
• updates BatchOriginTx field name tx_id to id and updates primary key to id,source
• adds missing origin_tx to EventCreateBatch (a batch may be created from a bridge event)
• adds EventMint for when credits are minted either as a result of creating a new batch (issuing credits) or dynamically minting credits to an existing batch (bridging credits)

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@2dfc570). Click here to learn what that means.
The diff coverage is 88.23%.

@@            Coverage Diff            @@
##             master    #1125   +/-   ##
=========================================
  Coverage          ?   64.02%           
=========================================
  Files             ?      215           
  Lines             ?    20332           
  Branches          ?        0           
=========================================
  Hits              ?    13018           
  Misses            ?     6045           
  Partials          ?     1269           

Flag	Coverage Δ
stable-codecov	64.02% <88.23%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

[aleem1314]

lgtm