[KT-69327] Correct FloatingPointParser.initialParse method to handle specific cases with invalid exponent string value

[OptimumCode]

Hi, this PR should close KT-69327 issue.

Unfortunately, I was not able to run tests: I executed ./gradlew install and then JAVA_OPTS=-Didea.sync.active=true ./gradlew -p libraries/stdlib nativeTest but got a compilation error related to classes in kotlin-native/runtime/src/main/kotlin directory.

If anyone knows how to execute the kotlin-native/runtime/test/text/StringNumberConversionNativeTest.kt test I would much appreciate it if you help me with that.

Please, let me know if anything else should be done in order to submit this PR.