Adopt inferred variable types (var) to enhance code readability and maintainability

[DennisDyallo]

Description

Now using inferred variable types (var) instead of explicit types in all projects except Yubico.Core. This change aims to improve code readability, reduce verbosity, and enhance developer productivity while maintaining type safety.

Key points:

• Improved readability: Using 'var' can make code more concise and easier to read, especially with long or complex type names.
• Reduced redundancy: 'var' eliminates the need to repeat type information that's already clear from the right-hand side of the assignment.
• Easier refactoring: When types change, using 'var' means fewer places in the code need to be updated.
• Consistency with modern C# practices: Many contemporary C# codebases and style guides recommend using 'var' where the type is obvious.
• Faster coding: Typing 'var' is quicker than writing out full type names, speeding up the development process.
• Encourages descriptive variable names: With type information inferred, developers are more likely to use clear, descriptive variable names.

Exclusion of Yubico.Core:
I excluded Yubico.Core from this change initially due to its extensive use of interop code and custom structs. This cautious approach allows us to implement the change gradually and assess its impact before applying it to more complex areas of the codebase.

By adopting 'var' in most of our projects, we aim to modernize our codebase, improve developer productivity, and enhance code maintainability while still maintaining the robustness and clarity of our type system.

Type of change

• Refactor (non-breaking change which improves code quality or performance)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

Unit tests in Yubico.Yubikey passed locally.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have run dotnet format to format my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

Test Results: Windows

    2 files      2 suites   5s ⏱️
3 703 tests 3 703 ✅ 0 💤 0 ❌
3 705 runs  3 705 ✅ 0 💤 0 ❌

Results for commit 6b971e6.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results: Ubuntu

    2 files      2 suites   10s ⏱️
3 695 tests 3 695 ✅ 0 💤 0 ❌
3 697 runs  3 697 ✅ 0 💤 0 ❌

Results for commit 6b971e6.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results: MacOS

    2 files      2 suites   4s ⏱️
3 695 tests 3 695 ✅ 0 💤 0 ❌
3 697 runs  3 697 ✅ 0 💤 0 ❌

Results for commit 6b971e6.

♻️ This comment has been updated with latest results.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Yubico.Core	42%	32%	4179	➖
Yubico.YubiKey	50%	47%	19110	➖
Summary	49% (32077 / 65925)	44% (8197 / 18549)	23289	➖

Minimum allowed line rate is 40%