support other_custom_types stellar example

[Islam-Imad]

closes #1960

[Copilot]

Pull request overview

This PR adds support for the Stellar Soroban other_custom_types example by porting the Solidity contract into the repository, documenting it in the Soroban examples coverage guide, adding a comprehensive Rust testcase suite, and fixing Soroban ABI enum encoding to match the spec.

Changes:

• Add other_custom_types Solidity example (both examples/ and docs/examples/) and document it in the Soroban examples coverage guide.
• Add a new Soroban testcase module with end-to-end ABI round-trip tests for primitives, enums, structs, vectors, events/auth, and error handling.
• Fix Soroban argument encoding for Solidity enums to use U32Val (unsigned) instead of I32Val, aligning with the ABI type (ScSpecTypeDef::U32) and the existing decode path.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/soroban_testcases/mod.rs	Registers the new example_other_custom_types testcase module.
tests/soroban_testcases/example_other_custom_types.rs	Adds end-to-end Soroban tests covering ABI round-trips, events/auth, and reverts for the example.
src/codegen/targets/soroban/encoding.rs	Fixes enum argument encoding to use unsigned U32Val tags per ABI.
examples/soroban/other_custom_types.sol	Adds the Solidity port of the upstream Soroban example for users/examples.
docs/examples/soroban/other_custom_types.sol	Adds the same Solidity port for documentation embedding/linking.
docs/targets/soroban_examples_coverage.rst	Documents the new example’s coverage and removes it from the “not yet documented” list.

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