Fix Instant parsing on Native being too lenient

[dkhalanskyjb]

[ilya-g]

First we need to discuss what behavior we want from Instant.parse. In java.time, for example, Instant.parse does support times like 23:59:60Z.

[dkhalanskyjb]

Closing in favor of #251

[ilya-g]

I believe we still should discuss how to address an inconsistency between platforms if there is any.

[dkhalanskyjb]

With #251, there isn't: the test from https://github.com/Kotlin/kotlinx-datetime/pull/251/commits/ca34c0abb0bbc935a7524d2ec24a84564a3e9972 passes for all platforms.

[ilya-g]

There's no inconsistency between platforms in kotlinx.datetime, but there's inconsistency between kotlinx.datetime and java.time in Instant.parse. Let's reopen.

[dkhalanskyjb]

Ok: #332