Fix amounts overflow

[Radiokot]

Purpose

This PR migrates all the amount-related long fields to BigInteger.

Currently, all the amounts are stored in long which is a 64-bit signed integer in Java. While it does the thing for small CCD amounts a typical user can face, CIS-2 tokens break it. In testnet, we have ETH.eth token with precision of 18. Having 100 ETH.eth on the balance overflows long and causes the wallet to crash.

Changes

• Migrated account balances, token balances, transaction amounts, etc. from long to BigInteger
• Migrated related database INTEGER fields to TEXT (auto migration)
• Added Gson and Room type adapters for BigInteger
• Fixed hardcoded 6 decimals in CurrencyUtil
• Fixed limit of 6 decimals in CurrencyUtil amount regex
• Added CurrencyUtil unit tests for extreme amounts
• Added balance test to the AccountDaoUnitTest

Checklist

• [x] My code follows the style of this project.
• [x] The code compiles without warnings.
• [x] I have performed a self-review of the changes.
• [x] I have documented my code, in particular the intent of the hard-to-understand areas.
• [x] (If necessary) I have updated the CHANGELOG.

CLA acceptance

_Remove if not applicable.

By submitting the contribution I accept the terms and conditions of the Contributor License Agreement v1.0

• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf

• [x] I accept the above linked CLA.

[czerwix]

please rebase PR

[Radiokot]

Conflicts with CIS-2 have been resolved