test(glyph): fix TS errors in glyph test files

- defineChart.test.tsx: cast formDataOverrides via `unknown` first
  because SqlaFormData (required datasource/viz_type) doesn't overlap
  with the looser Record<string, unknown> signature used in the test.
- generators.test.ts: add a glyphMap() helper to widen Map value type
  to `typeof Argument | GlyphArgConfig`. `new Map([...])` narrows from
  the first tuple, which broke mixed Metric/Checkbox entries.
- GlyphOptionsPanel.test.tsx: add `datasource: '1__table'` to every
  formData literal so they satisfy the SqlaFormData shape, and move
  imports above the jest.mock blocks to satisfy import/first.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>