[Refactor] PieChartStatisticViewModel: use by delegation for mutable states

[shamim-emon]

Please confirm the following

• I checked the current issues for duplicate issues.

What would you like to improve?

Rework val x = mutableStateOf() and x.value to x by mutableStateOf() and x.

Because...

It's more convenient to use and the code becomes simpler to read.

Description

No response

Success Criteria

• No functional changes
• The app works as expected

[ivywallet]

Thank you @shamim-emon for raising Issue #3526! 🚀
What's next? Read our Contribution Guidelines 📚.

Tagging @ILIYANGERMANOV for review & approval 👀

[shamim-emon]

I'm on it

[ivywallet]

Thank you for your interest @shamim-emon! 🎉
Issue #3526 is assigned to you. You can work on it! ✅

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