This adds string literals, number literals, `true`, `false`, `null` and
`undefined` to autocomplete results in templates.
For example, when completing an input of union type.
Component: `@Input('input') input!: 'a'|'b'|null;`
Template: `[input]="|"`
Provide `'a'`, `'b'`, and `null` as autocompletion entries.
Previously we did not include literal types because we only included
results from the component context (`ctx.`) and the template scope.
This is the second attempt at this. The first attempt is in
1d12c50f63 and it was reverted in 75f881e078150b0d095f2c54a916fc67a10444f6.
PR Close#41645
fe5bf7f53f