Add ledger/multisig detection in SignTx functions

[amaury1093]

Description

Before:
Some individual commands (tx sign, tx sign-batch) hardcoded to use SIGN_MODE_LEGACY_AMINO_JSON in the CLI command handler.

We forgot to hardcode SIGN_MODE_LEGACY_AMINO_JSON in the gentx command, hence the bug #9023

After:
Instead of putting the code:
if txF.SignMode == nil {txF.WithSignMode(LEGACY_AMINO_JSON)}
in each individual CLI command, we factorize that in the upstream .SignTx and .SignTxWithAddress functions that the CLI calls.

I tested simd gentx with a ledger key

closes: #9023

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• 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
• Review Codecov Report in the comment section below once CI passes

[amaury1093]

This function is called twice in the sdk, and both are with multisigs. As I understand, there's no use-case for calling this without a multisig, correct?

[aaronc]

That's probably right

[codecov]

Codecov Report

Merging #9026 (51e8df8) into master (feed37d) will decrease coverage by 0.10%.
The diff coverage is 12.50%.

❗ Current head 51e8df8 differs from pull request most recent head 41499bc. Consider uploading reports for the commit 41499bc to get more accurate results

@@            Coverage Diff             @@
##           master    #9026      +/-   ##
==========================================
- Coverage   58.96%   58.85%   -0.11%     
==========================================
  Files         575      573       -2     
  Lines       32159    32091      -68     
==========================================
- Hits        18963    18888      -75     
- Misses      10982    10992      +10     
+ Partials     2214     2211       -3     

Impacted Files	Coverage Δ
x/auth/client/tx.go	36.06% <0.00%> (-3.23%)	⬇️
x/auth/client/cli/tx_sign.go	73.88% <100.00%> (-0.71%)	⬇️
store/mem/store.go	60.00% <0.00%> (-21.82%)	⬇️
store/dbadapter/store.go	91.66% <0.00%> (-8.34%)	⬇️
store/rootmulti/store.go	66.05% <0.00%> (-2.42%)	⬇️
store/iavl/store.go	70.91% <0.00%> (-1.17%)	⬇️
store/tracekv/store.go	88.88% <0.00%> (-0.25%)	⬇️
store/gaskv/store.go	100.00% <0.00%> (ø)
store/types/store.go	60.00% <0.00%> (ø)
store/listenkv/store.go
... and 4 more

[aaronc]

ACK