Added summarize() API in DDS that generates summary tree and list of referenced routes

[agarwal-navin]

Fixes #3967

This is a pre-cursor to garbage collection.

• Garbage collection will re-use the data generated by snapshot for finding fluid objects that are referenced.
• Added a summarize() API in DDS to generate summary tree a list of routes to fluid objects referenced by it.
• I added a new IFluidSerializer implementation that can track the routes of handles that it serializes.
• DDSes uses this serializer to serialize its data during snapshot. The serializer tracks the routes of all handles in the data and this list is returned along with the snapshot tree.

A follow up PR will use the routes tracked during the snapshot process for use during GC.

[agarwal-navin]

@vladsud @anthony-murphy With this change, do we still need the IFluidSerializer at ContainerRuntime and DataStoreRuntime? I don't see them getting used in our code or in Bohemia's.

I do see that IFluidObject extends IProvideFluidSerializer but I am not sure if we need it.

[msfluid-bot]

■ @fluidframework/base-host: No change

Metric Name	Baseline Size	Compare Size	Size Diff
main.js	163.93 KB	163.93 KB	■ No change
Total Size	163.93 KB	163.93 KB	■ No change

⯅ @fluid-example/bundle-size-tests: +22.16 KB

Metric Name	Baseline Size	Compare Size	Size Diff
container.js	180.7 KB	181.91 KB	⯅ +1.21 KB
map.js	40.12 KB	46.25 KB	⯅ +6.12 KB
matrix.js	137.35 KB	144.78 KB	⯅ +7.43 KB
odspDriver.js	195.67 KB	195.67 KB	⯅ +1 Bytes
sharedString.js	150.89 KB	158.29 KB	⯅ +7.4 KB
Total Size	704.73 KB	726.89 KB	⯅ +22.16 KB

---

Baseline commit: a8e56c3

Generated by 🚫 dangerJS against 21f1f25

[anthony-murphy]

Fixes #3962

that doesn't look right. is it supposed to an issue

[agarwal-navin]

Fixes #3962

that doesn't look right. is it supposed to an issue

Updated it to reflect the correct issue.

[agarwal-navin]

@anthony-murphy Did I delete your comment in SharedObject? I was replying to it and I refreshed the page. Now, its gone!

[curtisman]

Closing and reopening to trigger build

[vladsud]

I must admit I reviewed it in chunks, between various commits, but overall looks good.

[agarwal-navin]

I must admit I reviewed it in chunks, between various commits, but overall looks good.

Thanks Vlad! We can keep iterating on it as and when needed.