Separate handler methods from context APIs as free functions

[Farhad-Shabani]

Closes: #539
Closes: #613

Basecoin CI check: 3dc0c23

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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

Patch coverage: 95.52% and project coverage change: -0.43 ⚠️

Comparison is base (7da7598) 73.29% compared to head (4d1ca0a) 72.86%.

❗ Current head 4d1ca0a differs from pull request most recent head 367a3b9. Consider uploading reports for the commit 367a3b9 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #661      +/-   ##
==========================================
- Coverage   73.29%   72.86%   -0.43%     
==========================================
  Files         122      113       -9     
  Lines       15588    15258     -330     
==========================================
- Hits        11425    11118     -307     
+ Misses       4163     4140      -23     

Impacted Files	Coverage Δ
crates/ibc/src/core/context.rs	63.04% <ø> (-13.18%)	⬇️
.../ibc/src/core/ics04_channel/handler/send_packet.rs	94.11% <ø> (ø)
...src/core/ics04_channel/handler/timeout_on_close.rs	88.01% <ø> (ø)
crates/ibc/src/core/handler.rs	88.60% <85.10%> (+13.60%)	⬆️
.../ibc/src/core/ics04_channel/handler/recv_packet.rs	92.96% <95.31%> (+1.10%)	⬆️
...bc/src/core/ics04_channel/handler/chan_open_ack.rs	97.50% <95.65%> (-0.92%)	⬇️
...rc/core/ics04_channel/handler/chan_open_confirm.rs	97.70% <95.78%> (-1.11%)	⬇️
...c/src/core/ics04_channel/handler/chan_open_init.rs	96.34% <96.36%> (-0.63%)	⬇️
...ates/ibc/src/core/ics04_channel/handler/timeout.rs	95.58% <96.44%> (-0.25%)	⬇️
...c/core/ics04_channel/handler/chan_close_confirm.rs	97.57% <96.49%> (-1.36%)	⬇️
... and 3 more

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[plafer]

👌