[Android] Add numeric-password variation to TextInputType (embedding) - #190207

…utter#190637)

Working towards flutter#190204.

Framework companion to the engine/embedding change in flutter#190207.

## Summary

Adds a `password` parameter to `TextInputType.numberWithOptions`,
symmetric to the existing `visiblePassword` text-class variation.

```dart
const TextInputType.numberWithOptions({
  this.signed = false,
  this.decimal = false,
  this.password = false,   // NEW
});
```

On Android this maps to
[`TYPE_NUMBER_VARIATION_PASSWORD`](https://developer.android.com/reference/android/text/InputType#TYPE_NUMBER_VARIATION_PASSWORD),
which the embedding now parses via `json.optBoolean("password", false)`
and ORs into the NUMBER branch of
`TextInputPlugin.inputTypeFromTextInputType` (flutter#190207). It has no effect
on iOS, web, or desktop.

`password: true` declares the **platform** input classification only. It
does not obscure the glyphs Flutter renders — that remains the
responsibility of `obscureText`.

## Backward compatibility

- Additive; default `false`; existing `TextInputType.number` and
`numberWithOptions(...)` callers are byte-for-byte unchanged.
- JSON is additive — older engines ignore the extra `password` key.
- No change to `obscureText`, `AutofillHints`, or
`enableIMEPersonalizedLearning` semantics.

`toJson`, `operator ==`, `hashCode`, `toString`, and dartdoc are updated
accordingly.

## Landing order

Per Tree Hygiene the engine JSON parsing + Android mapping (flutter#190207,
merged) lands first; this framework field follows once the engine
revision is rolled into the framework.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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[Data Driven Fixes]:
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…191244)

Working towards flutter#190204.

Follow-up to flutter#190207.

## Summary

Removes the 3-arg convenience constructor `InputType(type, isSigned,
isDecimal)` from `TextInputChannel.InputType`. Since flutter#190207 added
`isPassword`, the canonical constructor is the 4-arg one; the 3-arg
overload only remained for compatibility with existing test call sites,
which are now migrated to the 4-arg form with `isPassword = false`. This
matches `Configuration`, which keeps a single canonical constructor.

No production callers remain — `InputType.fromJson` was already the only
construction path in the embedding.

## Test Plan

- Existing `TextInputPluginTest` / `TextInputChannelTest` pass unchanged
in behavior (matrix tests already cover `isPassword` separately).
- Verified locally that both changed files compile against the embedding
classpath.

Co-authored-by: Camille Simon <[email protected]>