Fix mangled accents in Chocolatey output by decoding with the system console code page

[Gabriel Dufresne (GabrielDuf)]

This pull request improves how the application handles CLI output encodings for package managers, ensuring correct reading of console output from tools like Chocolatey that do not emit UTF-8. The main changes introduce a configurable OutputEncoding property for package managers, defaulting to UTF-8 but allowing overrides for managers that use the system console code page. The process start logic is updated to use this encoding, preventing character corruption in CLI output.

Encoding handling improvements:

• Added a ConsoleEncoding property to CoreData that detects and caches the system console code page, with a fallback to UTF-8 if detection fails.

• Updated the IPackageManager interface to include an OutputEncoding property, defaulting to UTF-8 but overridable by specific managers.

• The base PackageManager class and NullPackageManager now provide a default implementation for OutputEncoding.
  Chocolatey-specific changes:

• The Chocolatey package manager overrides OutputEncoding to use CoreData.ConsoleEncoding, ensuring correct output decoding for its CLI.

• All process invocations in Chocolatey and its helpers now use the manager's OutputEncoding for both standard output and error streams.

Dependency updates:

• Added the System.Text.Encoding.CodePages NuGet package to enable support for non-UTF-8 code pages.

Process invocation updates:

• All package operation process invocations now consistently use the package manager's OutputEncoding for output and error streams.