Upgrade hardhat version from 2.6 to 3.0 within /tools projects

[natanasow]

Problem

There are breaking changes between hardhat 2.6 and 3.0, which must be fixed manually.

Reference dependabot PRs:

• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/whbar-hardhat-example #4383
• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/hedera-crosschain-bridge #4382
• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/hardhat-example #4381
• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/subgraph-example #4380
• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/hardhat-viem-example #4379
• build(deps-dev): bump hardhat from 2.26.1 to 3.0.6 in /tools/solidity-coverage-example #4378

Solution

Migrate from hardhat 2.6 to 3.0.

Alternatives

No response

[acuarica]

IMO we shouldn't upgrade these. These should be kept in 2.x. Hardhat 2 and 3 are going to co-exist for a while given many projects are on HH 2. I don't see existing projects migrating from 2 to 3. My guess is that HH 3 will be used for new projects only.

That's why we should keep these on HH 2. And at most we can start including new projects under /tools with HH 3.

On the other hand, those dependabot PRs should be closed. Ideally, we should to exclude HH major upgrades from our dependabot.yaml config.