Removed GC blobs from channel context (DDS). The GC blobs in data store is used to generate initial GC data for DDS

[agarwal-navin]

Fixes #4943.

• Removed GC blobs from channel contexts (DDS).
• The GC blobs in the data store is now used to generate the initial GC data for channel contexts.
• The corresponding change in the FluidFrameworkTestData repo - Removed GC blobs from channel context's (DDS) summary FluidFrameworkTestData#11

Couple of notes:

• This change introduces a small inefficiency when a new DDS is created after the data store is attached. When the summarizer tries to get its GC data for the first time, it will generate the GC data even if there was no change in the DDS since it got the attach message. This is because the initial summary of the data store will not have the data for this DDS.
  • There is a simple fix for this - Add the GC blob to the DDS's summary only when creating attach message. However, this will introduce extra GC blobs in the initial summary which won't get removed until this DDS is summarized again. The inefficiency seems worth this trade-off. We can always add this if we realize that summarizing the DDS is becoming too expensive.
• Documents before this change won't have the getInitialGCSummaryDetails in IFluidChannelContext. So, the summarizer would end up summarizing these DDSs the first time. I can handle this scenario by adding some back-compat code but I don't think its worth maintaining that code for DDSs. Please let me know if you think we need to handle this scenario.

[vladsud]

Looks reasonable to me.

[vladsud]

I assume we have reasonable test coverage for new logic through existing UTs, right?

[agarwal-navin]

Unfortunately, we do not have unit tests for data store runtime! and for channel contexts too. We should definitely add those.

[agarwal-navin]

Created #5057 to add testing for these layers.

[msfluid-bot]

■ @fluidframework/base-host: No change

Metric Name	Baseline Size	Compare Size	Size Diff
main.js	169.41 KB	169.41 KB	■ No change
Total Size	169.41 KB	169.41 KB	■ No change

⯅ @fluid-example/bundle-size-tests: +1001 Bytes

Metric Name	Baseline Size	Compare Size	Size Diff
container.js	193.96 KB	194.94 KB	⯅ +1001 Bytes
map.js	45.92 KB	45.92 KB	■ No change
matrix.js	144.59 KB	144.59 KB	■ No change
odspDriver.js	195.89 KB	195.89 KB	■ No change
sharedString.js	158.65 KB	158.65 KB	■ No change
Total Size	739.01 KB	739.99 KB	⯅ +1001 Bytes

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Baseline commit: 96aaec4

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