Migrate to .NET 9

[rubo]

This PR is intended to be merged after .NET 9 general availability.
Some changes are temporary and will be reverted before merging.

Changes

• Set the target framework to net9.0
• Updated Docker files
• Updated .NET packages

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Runtime upgrade

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

Needs manual testing.

Documentation

Requires documentation update

• Yes
• No

NethermindEth/docs#225

Requires explanation in Release Notes

• Yes
• No