Add a saga pattern sample

[pavlo-v-chernykh]

What was changed

Add a saga pattern sample.

Why?

There is no saga pattern sample.

[CLAassistant]

All committers have signed the CLA.

[cretz]

For most use cases, saga seems to "just properly use defer" in Go. We even had a saga impl suggested as part of the SDK at temporalio/sdk-go#744 and we are still trying to decide how best to support saga pattern across SDKs at temporalio/features#50. I will confirm with others the value of this sample (I saw it was a TODO in the README) and get back.

We (kinda) document how to do a cleanup activity at https://pkg.go.dev/go.temporal.io/sdk/workflow#NewDisconnectedContext.

[pavlo-v-chernykh]

@cretz hi. Did you have a chance to talk with the team?

[cretz]

We can accept this, Can you sign the CLA?

[pavlo-v-chernykh]

@cretz, I'm glad to know.
I've signed the CLA.
Please, proceed.

[pavlo-v-chernykh]

@cretz, it looks like I do not have write access to this repository to merge the pull request. Please, merge it.