Add String(localized:) and String.LocalizationValue for Android

[piercifani]

Fixes skiptools/skip#538.

Native modules on Android have no String(localized:): swift-foundation on non-Darwin platforms doesn't ship String.LocalizationValue or the String(localized:) initializers. Today every module that wants them adds its own NSLocalizedString shim, and it has to be per-module because it calls the module-internal let NSLocalizedString = AndroidLocalizedString() generated in Bundle_Support.swift. String interpolation inside String(localized:) also can't work through such a shim: the shim receives the already-interpolated string as the lookup key.

This adds the missing API to SkipAndroidBridge, built on the existing AndroidStringInterpolation and AndroidLocalizedString:

• String.LocalizationValue (AndroidLocalizationValue)
• String(localized:table:bundle:locale:comment:)
• String(localized:defaultValue:table:bundle:locale:comment:)
• String(localized: LocalizedStringResource)

Notes:

• bundle: is typed AndroidBundle?, so bundle: .module resolves the module's synthesized Bundle.module (declared on AndroidBundle via the generated Bundle typealias).
• As on Darwin, the lookup key escapes a literal % as %% only when the string is interpolated ("100% done" → "100% done", "\(n)% done" → "%lld%% done"). Verified against Darwin Foundation.
• Compiled on every non-Darwin platform. On Android the lookup goes through AndroidBundle. On other hosts, such as the linux-gnu host pass of skip export, it uses Foundation.Bundle. Darwin, including a Robolectric host on macOS, keeps Foundation's implementation.
• Plural variations from .xcstrings are not handled, matching the transpiled String(localized:) in skip-foundation.

Testing

• New testStringLocalized sample test with an en.lproj/Localizable.strings (a .xcstrings is copied uncompiled by the swift.org toolchain with Xcode 16.4): literal keys, keys containing %, interpolation with positional arguments, untranslated fallback, defaultValue:, dynamic keys. It passes on macOS, where Foundation's implementation produces the same expected values. It is skipped on Robolectric on a macOS host, which runs Foundation's implementation and doesn't read the AndroidBundle strings.
• swift test (macOS + Robolectric) green; skip android build green.
• On-device: built a large consumer app (Polymarket, 9 native Skip modules) against this branch with its per-module shims deleted. All 8000 of its native tests pass on an arm64 emulator, including assertions on localized format output that now go through this API.

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