[Kotlin] Control the generation of reflection with --reflect-names (#7775)

* [Kotlin] Control the generation of reflection with --reflect-names.
Tested:
```
$ cmake -G "Unix Makefiles" && make && ./tests/flatc/main.py
...
KotlinTests.EnumValAttributes
 [PASSED]
KotlinTests.EnumValAttributes_ReflectNames
 [PASSED]
KotlinTests: 2 of 2 passsed
...

35 of 35 tests passed
```

* [Kotlin] Fix SampleBinary by converting Byte to UByte for ubyte fields.

* [Kotlin] Annotate all generated classes with kotlin.ExperimentalUnsignedTypes.

samples/SampleBinary.kt

@@ -24,6 +24,7 @@ import MyGame.Sample.Weapon
 
 import com.google.flatbuffers.FlatBufferBuilder
 
+@kotlin.ExperimentalUnsignedTypes
 class SampleBinary {
 
   companion object {
@@ -45,7 +46,7 @@ class SampleBinary {
 
         // Serialize the FlatBuffer data.
         val name = builder.createString("Orc")
-        val treasure = byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
+        val treasure = byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9).asUByteArray()
         val inv = Monster.createInventoryVector(builder, treasure)
         val weapons = Monster.createWeaponsVector(builder, weaps)
         val pos = Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f)
@@ -85,7 +86,7 @@ class SampleBinary {
 
         // Get and test the `inventory` FlatBuffer `vector`.
         for (i in 0 until monster.inventoryLength) {
-            assert(monster.inventory(i) == i.toByte().toInt())
+            assert(monster.inventory(i) == i.toUByte())
         }
 
         // Get and test the `weapons` FlatBuffer `vector` of `table`s.