feat: add coin argument to get_escrow_account method

[mina86]

To support blockchains and other systems where escrow account depends
on the coin being transferred (in addition to port and channel), add
coin argument to get_escrow_account.

Closes: #985

---

PR author checklist:

• Added changelog entry, using unclog.
• Added tests.
• Linked to GitHub issue.
• Updated code comments and documentation (e.g., docs/).
• Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
• Manually tested (in case integration/unit/mock tests are absent).

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (8f2ddfe) 70.76% compared to head (d5baa3a) 70.77%.

Files	Patch %	Lines
ibc-apps/ics20-transfer/src/handler/mod.rs	0.00%	2 Missing ⚠️
...-apps/ics20-transfer/src/handler/on_recv_packet.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #986   +/-   ##
=======================================
  Coverage   70.76%   70.77%           
=======================================
  Files         178      178           
  Lines       17943    17944    +1     
=======================================
+ Hits        12698    12699    +1     
  Misses       5245     5245           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Farhad-Shabani]

Hey @mina86, I somehow missed to update you on this PR. This is connected with PR #836 and it’s on our radar already. I’ll keep you posted as soon as we're out of there.