Integrate Swift Binary Parsing

[colemancda]

Summary

Integrates apple/swift-binary-parsing for safe, bounds-checked TLV8 parsing on Swift 6.2+ toolchains.

• TLVTypeCode, TLVItem, and TLVContainer conform to ExpressibleByParsing, adding throwing, span-based APIs: try TLVContainer(parsing: data) and incremental TLVItem(parsing: &input) consumption from a ParserSpan.
• TLVContainer.init(data:) is now backed by the BinaryParsing parser when the module is available; the hand-rolled parser remains as the fallback, so the public API and wire format are unchanged.
• The dependency follows the existing env-gate pattern: enabled by default on Swift 6.2+, disabled with SWIFTPM_ENABLE_BINARY_PARSING=0 (required for Embedded Swift builds, since the standard BinaryParsing product doesn't build for bare-metal triples).
• The Android emulator unit-test job is replaced with an x86_64 cross-compile check: SwiftPM's index-store-based XCTest discovery fails when cross-compiling a package whose test target uses macros (Cross-compiling packages which contain macros doesn't work swiftlang/swift-package-manager#6950), which has broken that job for every commit since the macros merge in Embedded Swift support #9.

Notes

• Apple deployment targets are raised to macOS 13 / iOS 16 / watchOS 9 / tvOS 16 when the dependency is enabled (its minimums).
• swift-binary-parsing 0.0.2 pins swift-syntax 602.0.0..<603.0.0, so the macros' swift-syntax version is forced to 602.0.0 when the gate is on. Their main already relaxed this to from: "602.0.0", so the pin can be dropped with their next release.
• All CI toolchains (macOS 26, Linux latest/nightly, Android 6.3.3, Windows 6.3.3) meet the Swift 6.2 requirement.

Test plan

• swift test — 9 tests pass, including new testBinaryParsing (span parsing, equivalence with init(data:), truncation errors)
• SWIFTPM_ENABLE_BINARY_PARSING=0 swift test — fallback parser path
• SWIFTPM_ENABLE_MACROS=0 swift build
• Embedded: SWIFTPM_ENABLE_MACROS=0 SWIFTPM_ENABLE_BINARY_PARSING=0 swift build --target TLVCoding --triple armv7em-none-none-eabi -Xswiftc -enable-experimental-feature -Xswiftc Embedded -Xswiftc -wmo