[Mono.Android] Add XML docs to KeyCharacterMap convenience overloads

[Copilot]

The two public convenience overloads in src/Mono.Android/Android.Views/KeyCharacterMap.cs ship in Mono.Android.dll without XML documentation. Both are managed overloads that take the meta-key state as an int and delegate to the strongly-typed MetaKeyStates overloads, so they have no base/interface docs to inherit.

Changes

• Added /// XML documentation (<summary>, <param>, <returns>, <seealso href>) to Get (Keycode, int) and GetMatch (Keycode, char[], int).
• Followed the existing doc style from Android.Util/Log.cs; <see cref="MetaKeyStates"/> resolves unqualified since it shares the Android.Views namespace.
• Docs-only: no signatures, logic, using directives, or #nullable enable touched.

/// <summary>
/// Gets the Unicode character generated by the specified key and meta key state combination.
/// </summary>
/// <param name="keyCode">The key code.</param>
/// <param name="metaState">A combination of <see cref="MetaKeyStates"/> values, expressed as an integer.</param>
/// <returns>The Unicode character (code point) produced by the key, or <c>0</c> if the key does not produce a character.</returns>
/// <seealso href="https://developer.android.com/reference/android/view/KeyCharacterMap#get(int,%20int)">Android documentation for <c>android.view.KeyCharacterMap.get</c></seealso>
public int Get (Keycode keyCode, int metaState)

[Copilot]

Pull request overview

Adds missing XML documentation to the two public convenience overloads on Android.Views.KeyCharacterMap that accept metaState as an int, aligning them with existing documentation patterns used elsewhere in Mono.Android (notably Android.Util.Log).

Changes:

• Added <summary>, <param>, and <returns> docs for Get (Keycode, int) and GetMatch (Keycode, char[], int).
• Added MetaKeyStates references in parameter docs to clarify the meaning of the integer metaState.
• Added <seealso href="..."> links to the corresponding Android reference documentation pages.