Default back to old SCardConnect behavior

[GregDomzalski]

Description

Reverts the change in behavior to open smart card handles exclusively. Instead now defaults back to shared like it was before, but allows for applications to toggle between the new and old behavior through the use of AppContext.SetSwitch.

Fixes #72 and probably #81 as well.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

Wrote some test code using the TestApp and verified:

• No compat flag present = SHARED
• Flag present & false = SHARED
• Flag present & true = EXCLUSIVE

Test configuration:

• Firmware version: 5.4.3
• Yubikey model: ANFC

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   2s ⏱️
3 615 tests 3 615 ✅ 0 💤 0 ❌
3 617 runs  3 617 ✅ 0 💤 0 ❌

Results for commit 9ceeb6a.

[github-actions]

Test Results: Ubuntu

    2 files      2 suites   5s ⏱️
3 607 tests 3 607 ✅ 0 💤 0 ❌
3 609 runs  3 609 ✅ 0 💤 0 ❌

Results for commit 9ceeb6a.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Yubico.Core	42%	32%	4245	➖
Yubico.YubiKey	51%	47%	18417	➖
Summary	49% (31675 / 64299)	45% (8017 / 17967)	22662	➖

Minimum allowed line rate is 40%

[github-actions]

Test Results: MacOS

    2 files      2 suites   1s ⏱️
3 607 tests 3 607 ✅ 0 💤 0 ❌
3 609 runs  3 609 ✅ 0 💤 0 ❌

Results for commit 9ceeb6a.

[DennisDyallo]

LGTM

[DennisDyallo]

Although I would've preferred dependency injection I agree this is the least intrusive change 👍