Use TestDAppV2 for all E2E tests needing a test contract

[lumtis]

Describe the Issue

#2639 introduces a test contract for V2 E2E tests.

We currently have different test contracts:

• context dapp
• testdappv1
• swap contract

Would be easier to only keep a single smart contract supporting all uses case and having only this one to keep in the config.

This task is about consolidating all test contracts in E2E in a single one.

[lumtis]

Will be completed by removing legacy contract, new tests use new contracts