Replace string concat ABI gen with serde structs and abi_param()

[smiasojed]

No description provided.

[github-actions]

Benchmark Size Comparison (vs main)

Artifact	Baseline	Current	Delta	Status
fibonacci_builder-dsl.debug.polkavm	36890	36890	+0.00%	OK
fibonacci_builder-dsl.release.polkavm	1193	1193	+0.00%	OK
fibonacci_no-alloc.debug.polkavm	35986	35986	+0.00%	OK
fibonacci_no-alloc.release.polkavm	469	469	+0.00%	OK
fibonacci_with-alloc.debug.polkavm	46400	46400	+0.00%	OK
fibonacci_with-alloc.release.polkavm	448	448	+0.00%	OK
multi_builder-dsl.debug.polkavm	54064	54064	+0.00%	OK
multi_builder-dsl.release.polkavm	3565	3565	+0.00%	OK
multi_no-alloc.debug.polkavm	55396	55396	+0.00%	OK
multi_no-alloc.release.polkavm	3272	3272	+0.00%	OK
multi_with-alloc.debug.polkavm	66808	66808	+0.00%	OK
multi_with-alloc.release.polkavm	3749	3749	+0.00%	OK
mytoken_builder-dsl.debug.polkavm	50188	50196	+0.02%	OK
mytoken_builder-dsl.release.polkavm	4096	4096	+0.00%	OK
mytoken_no-alloc.debug.polkavm	52396	52396	+0.00%	OK
mytoken_no-alloc.release.polkavm	3674	3674	+0.00%	OK
mytoken_with-alloc.debug.polkavm	64436	64436	+0.00%	OK
mytoken_with-alloc.release.polkavm	4267	4267	+0.00%	OK
----------------------------------------------------	------------	------------	----------	--------
Total	487297	487305	+0.00%

OK: All artifacts within 5% regression threshold

_{Run 24249362098 | c8c848e | 2026-04-10 15:25 UTC}