Add API for compatible query of two types of transactions

[summerpro]

Closes: #630

Description

---

For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

---

For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[fedekunze]

Looks good! See the first comment for another proposed approach

[summerpro]

why deploy contract test failed ?

[summerpro]

@fedekunze Can this pr be merged?

[fedekunze]

untested ACK

[araskachoi]

What was this supposed to fix? I'm thinking that this was a way to interpret the EthereumTxMsg that was generated from a transaction using RPC when querying the tx hash using curl localhost:8545/txs/{HASH}...?
If so, I have just tried doing this and it still gives the parsing err (internal error: tx {HASH} not found). This is probably related to #630 and may require a better way of decoding the amino msg or removing the EtheremintMsg altogether.
Can we discuss? Thanks!