Illia malachyn/763 refactor mock stream objects

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 71 lines in your changes missing coverage. Please review.

Project coverage is 55.14%. Comparing base (c8d6c13) to head (1ce4e70). Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
access/grpc/convert/convert.go	0.00%	31 Missing :warning:
access/grpc/client.go	0.00%	22 Missing :warning:
access/grpc/grpc.go	88.75%	9 Missing and 9 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #775 +/- ## ========================================== + Coverage 52.38% 55.14% +2.76% ========================================== Files 35 35 Lines 5559 5759 +200 ========================================== + Hits 2912 3176 +264 + Misses 2261 2133 -128 - Partials 386 450 +64 ``` | [Flag](https://app.codecov.io/gh/onflow/flow-go-sdk/pull/775/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/onflow/flow-go-sdk/pull/775/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow) | `55.14% <66.66%> (+2.76%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow#carryforward-flags-in-the-pull-request-comment) to find out more.

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[illia-malachyn]

will make it ready for review after we merge all dependent issues

[illia-malachyn]

it's easier to make changes on a new master, so I'm closing this and will open a new PR