Add string interpolation support in codegen

[sofurihafe]

Description

This PR adds string interpolation support for Java and Kotlin codegen.

Fixes # (1546)

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Regression and integration tests

Automated Testing

utbot-samples.

Manual Scenario

Usage example:

CgFormattedString(
    listOf(
        stringLiteral("Custom message:"),
        actual,
        stringLiteral("has to be"),
        expected
    )
)

It will produce the following results:
For Java:

String.format("Custom message: %s has to be 1", actual)

For Kotlin:

"Custom message: $actual has to be 1"