chore(rust/signed-doc): Making tests/common module as a public mod catalyst_signed_doc::tests_utils

[Mr-Leshiy]

Description

Refactor catalyst-signed-doc tests utilities code, moving it as a public mod catalyst_signed_doc::tests_utils.

Related Issue(s)

Needed for #691

Description of Changes

• Deleted tests/common mod, moved all the code to the catalyst_signed_doc::tests_utils.
• Removed duplicated create_dummy_key_pair, create_dummy_doc_ref.
• Split create_dummy_key_pair(Option<RoleId>) to create_dummy_key_pair(RoleId) and create_dummy_admin_key_pair
• Updated existing tests.

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

📚 Docs Preview

The docs for this PR can be previewed at the following URL:

https://docs.dev.projectcatalyst.io/libs/feat/refactor-tests

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 633/633}$ | ${\color{red}Fail: 0/633}$ |