Improved unit tests to eliminate spurious failures

[tombogle]

These tests formerly relied on clipboard access or Application.DoEvents and actual mouse positions and timing.

---

This change is 

[github-actions]

LibPalaso Tests

    45 files  ± 0      45 suites  ±0   9m 22s ⏱️ - 2m 33s
 4 843 tests +13   4 612 ✅ +13  231 💤 ±0  0 ❌ ±0 
14 034 runs  +26  13 407 ✅ +26  627 💤 ±0  0 ❌ ±0 

Results for commit 9b80557. ± Comparison against base commit de37405.

♻️ This comment has been updated with latest results.

[andrew-polk]

Reviewed 2 of 3 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @tombogle)

[github-actions]

Palaso Tests

     3 files  ± 0       3 suites  ±0   17m 58s ⏱️ + 1m 42s
 4 837 tests +13   4 606 ✅ +14  231 💤 ±0  0 ❌  - 1 
14 022 runs  +26  13 395 ✅ +27  627 💤 ±0  0 ❌  - 1 

Results for commit e0b575b. ± Comparison against base commit 1c95083.

[andrew-polk]

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @tombogle)

[andrew-polk]

Dismissed @josephmyers from a discussion.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @tombogle)

[andrew-polk]

Dismissed @tombogle from a discussion.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @tombogle)

He is not available and his concern was addressed.