Mosa.DeviceDriver: clean up pointless types + other minor changes

[AnErrupTion]

This PR focuses on cleaning up pointless and/or unused types in the Mosa.DeviceDriver project. The following changes were done:

• Removed X86System since it was only initializing ISABus
• Removed GenericHostBridgeController and IHostBridgeController since they were only used for the 2nd ACPI reset method, except it never worked anyway

In addition, the following changes were also done:

• Updated the copyright year to 2024
• Updated the assembly version in Directory.Build.props to 2.6.0.0
• Improved the StringBuilder implementation
• Implemented String.Format() to fix non-working string interpolation in the kernel
• Implemented Char.IsAsciiDigit() as a shortcut to Char.IsDigit()
• Removed DataBlock.this[] since it was not only unused but also ambiguous (what data type should/would it return?)