[core] use StringComparer for Dictionary/HashSet (#14900)

Context: dotnet/maui#12130
Context: https://github.com/angelru/CvSlowJittering

When profiling the above customer app while scrolling, 4% of the time
is spent doing dictionary lookups:

    (4.0%) System.Private.CoreLib!System.Collections.Generic.Dictionary<TKey_REF,TValue_REF>.FindValue(TKey_REF)

Observing the call stack, some of these are coming from culture-aware
string lookups in MAUI:

* `microsoft.maui!Microsoft.Maui.PropertyMapper.GetProperty(string)`
* `microsoft.maui!Microsoft.Maui.WeakEventManager.AddEventHandler(System.EventHandler`1<TEventArgs_REF>,string)`
* `microsoft.maui!Microsoft.Maui.CommandMapper.GetCommand(string)`

Which show up as a mixture of `string` comparers:

    (0.98%) System.Private.CoreLib!System.Collections.Generic.NonRandomizedStringEqualityComparer.OrdinalComparer.GetHashCode(string)
    (0.71%) System.Private.CoreLib!System.String.GetNonRandomizedHashCode()
    (0.31%) System.Private.CoreLib!System.Collections.Generic.NonRandomizedStringEqualityComparer.OrdinalComparer.Equals(string,stri
    (0.01%) System.Private.CoreLib!System.Collections.Generic.NonRandomizedStringEqualityComparer.GetStringComparer(object)

In cases of `Dictionary<string, TValue>` or `HashSet<string>`, we can
use `StringComparer.Ordinal` for faster dictionary lookups.

Unfortunately, there is no code analyzer for this:

dotnet/runtime#52399

So, I manually went through the codebase and found all the places.

I now only see the *fast* string comparers in this sample:

    (1.3%) System.Private.CoreLib!System.Collections.Generic.NonRandomizedStringEqualityComparer.OrdinalComparer.GetHashCode(string)
    (0.35%) System.Private.CoreLib!System.Collections.Generic.NonRandomizedStringEqualityComparer.OrdinalComparer.Equals(string,stri

Which is about ~0.36% better than before.

This should slightly improve the performance of handlers & all
controls on all platforms.

I also fixed `Microsoft.Maui.Graphics.Text.TextColors` to use
`StringComparer.OrdinalIgnoreCase` -- and removed a
`ToUpperInvariant()` call.

src/TextToSpeech/TextToSpeech.android.cs

@@ -157,7 +157,7 @@ public async Task SpeakAsync(string text, int max, SpeechOptions options, Cancel
 			for (var i = 0; i < parts.Count && !cancelToken.IsCancellationRequested; i++)
 			{
 				// We require the utterance id to be set if we want the completed listener to fire
-				var map = new Dictionary<string, string>
+				var map = new Dictionary<string, string>(StringComparer.Ordinal)
 				{
 					{ AndroidTextToSpeech.Engine.KeyParamUtteranceId, $"{guid}.{i}" }
 				};

src/Types/Shared/WebUtils.shared.cs

@@ -10,7 +10,7 @@ static class WebUtils
 	{
 		internal static IDictionary<string, string> ParseQueryString(string url)
 		{
-			var d = new Dictionary<string, string>();
+			var d = new Dictionary<string, string>(StringComparer.Ordinal);
 
 			if (string.IsNullOrWhiteSpace(url) || (url.IndexOf("?", StringComparison.Ordinal) == -1 && url.IndexOf("#", StringComparison.Ordinal) == -1))
 				return d;

src/VersionTracking/VersionTracking.shared.cs

@@ -238,15 +238,15 @@ internal void InitVersionTracking()
 			IsFirstLaunchEver = !preferences.ContainsKey(versionsKey, sharedName) || !preferences.ContainsKey(buildsKey, sharedName);
 			if (IsFirstLaunchEver)
 			{
-				versionTrail = new Dictionary<string, List<string>>
+				versionTrail = new(StringComparer.Ordinal)
 				{
 					{ versionsKey, new List<string>() },
 					{ buildsKey, new List<string>() }
 				};
 			}
 			else
 			{
-				versionTrail = new Dictionary<string, List<string>>
+				versionTrail = new(StringComparer.Ordinal)
 				{
 					{ versionsKey, ReadHistory(versionsKey).ToList() },
 					{ buildsKey, ReadHistory(buildsKey).ToList() }

src/WebAuthenticator/WebAuthenticatorResult.shared.cs

@@ -73,7 +73,7 @@ public WebAuthenticatorResult(IDictionary<string, string> properties)
 		/// <summary>
 		/// The dictionary of key/value pairs parsed form the callback URI's query string.
 		/// </summary>
-		public Dictionary<string, string> Properties { get; set; } = new Dictionary<string, string>();
+		public Dictionary<string, string> Properties { get; set; } = new(StringComparer.Ordinal);
 
 		/// <summary>Puts a key/value pair into the dictionary.</summary>
 		public void Put(string key, string value)