Provide a Coroutine variant of ScanStream/ScanIterator

[sokomishalov]

Implements #1435

P.S. Actually I'm not sure about the extension's signature due to the compiler conflict with existing member methods.
It makes end-users provide import aliases (see ScanStreamCoroutinesIntegrationTests).
Also maybe we should not underly on the ScanStream and provide separate and independent one.

[codecov]

Codecov Report

Merging #1438 into main will decrease coverage by 0.03%.
The diff coverage is 82.05%.

@@             Coverage Diff              @@
##               main    #1438      +/-   ##
============================================
- Coverage     78.82%   78.79%   -0.04%     
- Complexity     6183     6219      +36     
============================================
  Files           460      462       +2     
  Lines         20800    20774      -26     
  Branches       2302     2295       -7     
============================================
- Hits          16396    16369      -27     
- Misses         3338     3345       +7     
+ Partials       1066     1060       -6     

Impacted Files	Coverage Δ	Complexity Δ
...pi/coroutines/RedisCoroutinesCommandsExtensions.kt	0.00% <0.00%> (ø)	0.00 <0.00> (?)
src/main/kotlin/io/lettuce/core/ScanFlow.kt	61.29% <61.29%> (ø)	10.00 <10.00> (?)
...i/coroutines/RedisClusterCoroutinesCommandsImpl.kt	81.25% <92.85%> (ø)	1.00 <1.00> (?)
...tuce/core/api/StatefulRedisConnectionExtensions.kt	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
.../api/coroutines/BaseRedisCoroutinesCommandsImpl.kt	5.55% <100.00%> (ø)	1.00 <1.00> (?)
...core/api/coroutines/RedisCoroutinesCommandsImpl.kt	78.94% <100.00%> (ø)	2.00 <2.00> (?)
...e/api/coroutines/RedisGeoCoroutinesCommandsImpl.kt	8.33% <100.00%> (ø)	1.00 <1.00> (?)
...e/api/coroutines/RedisHLLCoroutinesCommandsImpl.kt	25.00% <100.00%> (ø)	1.00 <1.00> (?)
.../api/coroutines/RedisHashCoroutinesCommandsImpl.kt	10.00% <100.00%> (ø)	2.00 <1.00> (?)
...e/api/coroutines/RedisKeyCoroutinesCommandsImpl.kt	2.85% <100.00%> (ø)	1.00 <1.00> (?)
... and 41 more

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[mp911de]

Moving this into the next iteration. Will review this PR after the release of 6.0.

[mp911de]

I added two comments, one about the overall design, one about splitting this PR into two commits to keep commits focussed on the actual topic.

[mp911de]

I'm going to take this PR from here.

[mp911de]

Thank you for your contribution. That's merged and polished now.