[Chore] tag v3.5.0 (20230530) #227

Commits from v3.4.1 to v3.5.0

* New feature
1. [Feature&refinement] implement new multiple ECU OTA update spec, refactoring otaclient_stub module #212

* Bug fix
1. [Fix] delta calculating: verify file when copying from active slot to standby slot #211
2. [Fix] fix downloader last_active_timestamp recording #213
3. [Fix&refine] retry inifinitely on metadata.jwt and certificate downloading error #215
4. [Fix] ecu_info: not loading default config when ecu_info.yaml is invalid in some cases #217
5. [Fix & Refinement] ota_metadata: implement validation over metadata.jwt #222

* Refinement
1. [Refine] otaproxy: suppress flooding loggings when network disconnected #214
2. [Refinement] refinement related to otaproxy launching #218
3. [Refinement] common: add ensure_otaproxy_start for probing otaproxy online #219
4. [Fix & Refinement] ota_metadata: implement validation over metadata.jwt #222
5. [Refinement] cleanup ota_client_service.py, implement test file #221
6. [Refinement] align and regulate each call's behavior in otaclient_call module #224
7. [Feature&refinement] implement new multiple ECU OTA update spec, refactoring otaclient_stub module #212

* Chore
1. [Chore] Add PR templates #220
2. [Chore] update .flake8 and pyproject.toml for linting configuration #223

* Deps
1. Bump requests from 2.25.1 to 2.31.0 in /otaclient #226

Author: obi-t4