common : add gemma 4 specialized parser (#21418)

common : add gemma 4 specialized parser (#21418)

* common : add gemma4 dedicated parser

* cont : add '<|tool_response>' as eog

* cont : emit JSON from Gemma4 tool call AST

* cont : more fixes

* cont : refactor convert function

* cont : refine rules and mapping

* cont : add more tests

* cont : clean up

* cont : remove autoparser gemma4 implementation

* cont : more cleanup

* cont : rename gemma4.jinja to match the others

* cont : add custom template to support interleaved thinking

* cont : preserve reasoning in model turns

* cont : fix initializer error

* cont : fix unused vars

* cont : fix accidental static

* cont : fix specialized_template signature

* fix extra semicolon

* remove debug line and extra space [no ci]