[refactor]: move instruction len from data_model into core

[mversic]

Description

the less functionality we expose in public API the better

Linked issue

Closes #{issue_number}

Benefits

Checklist

• I've read CONTRIBUTING.md
• I've used the standard signed-off commit format (or will squash just before merging)
• All applicable CI checks pass (or I promised to make them pass later)
• (optional) I've written unit tests for the code changes
• I replied to all comments after code review, marking all implemented changes with thumbs up

[coveralls]

Pull Request Test Coverage Report for Build 5589398667

• 74 of 121 (61.16%) changed or added relevant lines in 11 files are covered.
• 2153 unchanged lines in 46 files lost coverage.
• Overall coverage decreased (-0.09%) to 59.345%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
core/src/smartcontracts/isi/world.rs	0	1	0.0%
core/src/smartcontracts/isi/triggers/mod.rs	0	2	0.0%
core/src/smartcontracts/isi/asset.rs	0	3	0.0%
data_model/src/visit.rs	0	3	0.0%
data_model/derive/src/model.rs	0	4	0.0%
core/src/tx.rs	65	77	84.42%
wasm_codec/derive/src/lib.rs	4	26	15.38%

Files with Coverage Reduction	New Missed Lines	%
client_cli/src/main.rs	1	0%
client/src/http_default.rs	1	0%
cli/src/main.rs	1	0%
core/src/smartcontracts/isi/asset.rs	1	29.79%
core/src/sumeragi/network_topology.rs	1	96.77%
data_model/src/name.rs	1	94.25%
derive_primitives/src/lib.rs	1	0%
macro/derive/src/lib.rs	1	94.59%
wasm_codec/derive/src/lib.rs	1	86.18%
cli/derive/src/lib.rs	5	93.14%

Totals
Change from base Build 5423219773:	-0.09%
Covered Lines:	19851
Relevant Lines:	33450

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💛 - Coveralls

[appetrosyan]

TRYBUILD=overwrite and it should work.