* Change 1.6 to 1.7 constants
* Fix SAFE_CALL_WILL_CHANGE_NULLABILITY for testData
* Change EXPOSED_PROPERTY_TYPE_IN_CONSTRUCTOR_WARNING to EXPOSED_PROPERTY_TYPE_IN_CONSTRUCTOR_ERROR
* Change NON_EXHAUSTIVE_WHEN_STATEMENT to NO_ELSE_IN_WHEN
* Fix testData for SafeCallsAreAlwaysNullable
* Change T -> T & Any in test dumps
* Change INVALID_CHARACTERS_NATIVE_WARNING -> INVALID_CHARACTERS_NATIVE_ERROR
* TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM_WARNING -> TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM_ERROR
FIR translates:
```
when (x) {
1, 2, 3 -> action
else -> other_action
}
```
to an IR structure with nested ors:
```
if ((x == 1 || x == 2) || (x == 3)) action
else other_action
```
This change allows that to turn into switch instructions in the
JVM backend.
Otherwise some tools break (e.g. CheckMethodAdapter in ASM, used in generic
signature writer) because they expect class names to be Java identifiers.
Some tests fixed, some will be fixed in future commits
Mikhail Glukhikh