[Feat]: Upgrade A2A to v1.0

[Tehsmash]

Is your feature request related to a problem? Please describe.

A2A v1.0 is coming, we need to upgrade the SDK to support that specification

Describe the solution you'd like

Refactor the SDK to use the new v1.0 version of the specification

Describe alternatives you've considered

N/A

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[ishymko]

Hey @muscariello, @Tehsmash, wanted to check on #572 (great work BTW, thanks a lot!). If I understand correctly the next step is to merge 1.0-a2a_proto_refactor into 1.0-dev? Will you be able to take it? Please let me know if anything is needed and also send PRs my way.

Thank you!

FYI: I've merged main into 1.0-dev recently (#658) and enabled linter and unit tests in CI.