Add tests for elide imports and fix named imports with default imports

[alan-agius4]

• test: add tests for elide imports
  This also adds the option to provide addition files when using createTypescriptContext this is paramount for the elide imports tests as without this certain symbols won't have the full details.

Which will cause tests to be false positive and re-surface issues like #13212

• fix(@ngtools/webpack): drop only unused default import when used with… …
  … named imports

At the moment when having a default import together with a named import example:

import abc, { def } from './foo';

And the default import becomes unused it will drop the entire node which will caused used named imports to be dropped as well.

• refactor: use getExportSpecifierLocalTargetSymbol and getShorthandAssignmentValueSymbol to handle symbols lookups

Use typechecker methods to handle special cases for ExportSpecifier and ShorthandPropertyAssignment

[ngbot]

	Artifact	Baseline	Current	Change
❕	cli/new-production/test-project/main.js	175.29KB	175.29KB	+3 bytes

[clydin]

nice work. 👍

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