Fix Kimi-K2 tool-call parsing issues (#17376)
* Fix kimi-k2 parsing
* fix template & add more tests for kimi-k2
* Another fix for Kimi-K2 chat template.
* enable allow_toolcall_in_think for Kimi-K2
* Refine key-value separator and value end format
* Enable tool call in think for kimi-k2
* allow_toolcall_in_think is now tested with Kimi-K2
* Remove outdated TODO comment in XML tool call parser
Removed TODO comment about untested tool call feature.
* Rename function from "utf8_truncate_safe" to "utf8_truncate_safe_len"
