LT-21669: Use WS numbers for headword numbers

[aror92]

• Remove option to add custom numbers from dictionary configuration > headword numbers. Instead, get the numbering system associated with the WS selected for headword numbers and display these numbers in the headword numbers configuration.
• Ensure the WS numbering system is used for homograph/sense numbers in ConfiguredLCMGenerator.
• In the Configure Headword Numbers dlg, use Winforms labels for number display instead of Fwtextboxes, which don't display all glyphs correctly.
• Update WS custom number handling to include the case when a drop-down preset is selected by the user, instead of typed in custom numbers.
• Handle UTF-16 surrogate pairs via GetUnicodeCharacters helper function in new HeadWordNumbersHelper class.
• Update expected behavior in tests related to headword numbers.
• Remove tests related to setting custom headword numbers, since this is no longer allowed.

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This change is 

[github-actions]

NUnit Tests

    1 files  ±0      1 suites  ±0   6m 12s ⏱️ -16s
4 102 tests  - 1  4 031 ✅  - 1  71 💤 ±0  0 ❌ ±0 
4 111 runs   - 1  4 040 ✅  - 1  71 💤 ±0  0 ❌ ±0 

Results for commit f1f2c3e. ± Comparison against base commit 5334190.

This pull request removes 3 and adds 2 tests. Note that renamed tests count towards both.

SIL.FieldWorks.XWorks.HeadwordNumbersControllerTests ‑ ConstructorSetsCustomHeadwordNumbersInView
SIL.FieldWorks.XWorks.HeadwordNumbersControllerTests ‑ Ok_Disabled_WhenNotAllTenNumbersSet
SIL.FieldWorks.XWorks.HeadwordNumbersControllerTests ‑ Ok_Enabled_WithAllTenNumbers

SIL.FieldWorks.XWorks.HeadwordNumbersControllerTests ‑ ConstructorSetsHeadwordWritingSystemNumbersInView
SIL.FieldWorks.XWorks.HeadwordNumbersControllerTests ‑ CustomDigits_Default_Ok_Enabled_WhenNotAllTenNumbersSet

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