NotEmptySet to inline class

[LVMVRQUXL]

Description

Like discussed in the issue #97, we would like to convert the NotEmptySet type to an inline class.

This is breaking change: the copy function will be unavailable after this migration.

Checklist

• Add unit tests for the equals function.
• Migrate the type to an inline class without breaking its API (except for the copy function).
• Improve the type's documentation.
• Check the generated documentation.
• Check and update the public API binaries.
• Update the Unreleased section in changelog.
• Refactor the construction of NotEmptySet.
• Update the type's documentation.
• Update all tests of this type.

[LVMVRQUXL]

See the issue #136 and the PR #145 for more information about how to convert this type to an inline class.

[LVMVRQUXL]

We need to refactor the construction of the NotEmptySet for better performance.
Please note that changes made to the original collection should not be reflected to the resulting NotEmptySet.

val original: MutableSet<Int> = mutableSetOf(1, 2, 3, 1)
val notEmptySet: NotEmptySet<Int> = original.toNotEmptySet()
    .getOrThrow()
println(original) // [1, 2, 3]
println(notEmptySet) // [1, 2, 3]

original.clear()
println(original) // []
println(notEmptySet) // [1, 2, 3]