[android] compute HasRtlSupport once on startup

[jonathanpeppers]

Description of Change

Previously we were calculating:

public static bool HasRtlSupport(this Context self)
{
    if (self == null)
        return false;

    return (self.ApplicationInfo?.Flags & AApplicationInfoFlags.SupportsRtl) == AApplicationInfoFlags.SupportsRtl;
}

Multiple times for every Label, Entry, or related controls.
Context.ApplicationInfo pulls values from the AndroidManifest.xml
for the entire Android application, so this isn't a value that would
not change after startup -- or for different controls.

https://developer.android.com/reference/android/content/pm/ApplicationInfo#flags
https://developer.android.com/reference/android/content/pm/ApplicationInfo#FLAG_SUPPORTS_RTL

Let's move this method to be a static readonly field in a new static
class. It will lazily be evaluated when the new class is accessed, and
only once per application run.

Results

Running ViewHandlerBenchmark on a Pixel 5 device:

> .\bin\dotnet\dotnet build .\src\Core\tests\Benchmarks.Droid\Benchmarks.Droid.csproj -t:Benchmark -c Release

Method	Mean	Error	StdDev	Gen 0	Allocated
-Label	527.6 µs	4.89 µs	4.57 µs	0.9766	5 KB
+Label	494.9 µs	5.72 µs	5.35 µs	0.9766	5 KB
-Entry	1,951.2 µs	5.02 µs	4.19 µs	-	12 KB
+Entry	1,925.8 µs	13.24 µs	11.74 µs	-	12 KB

- Using dotnet/maui/main before these changes
+ Using these changes

I tried a few times, and I'm not sure I'm able to see a measurable
difference launching Maui.Controls.Sample.SingleProject.csproj over
and over. But this change seems low risk, worth adding in.

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)
• Targets a single property for a single control (or intertwined few properties)
• Adds the property to the appropriate interface
• Avoids any changes not essential to the handler property
• Adds the mapping to the PropertyMapper in the handler
• Adds the mapping method to the WinUI, Android, iOS, and Standard aspects of the handler
• Implements the actual property updates (usually in extension methods in the Platform section of Core)
• Tags ported renderer methods with [PortHandler]
• Adds an example of the property to the sample project (MainPage)
• Adds the property to the stub class
• Implements basic property tests in DeviceTests

Does this PR touch anything that might affect accessibility?

No