common/parser: handle reasoning budget (#20297)

* v1

* Finished!

* Handlie cli

* Reasoning sampler

* Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Less explosive terminology :)

* Add utf-8 case and tests

* common : migrate reasoning budget sampler to common

* cont : clean up

* cont : expose state and allow passing as initial state

* cont : remove unused imports

* cont : update state machine doc string

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>
Co-authored-by: Alde Rojas <hello@alde.dev>

common/CMakeLists.txt

@@ -81,6 +81,8 @@ add_library(${TARGET} STATIC
     preset.cpp
     preset.h
     regex-partial.cpp
+    reasoning-budget.cpp
+    reasoning-budget.h
     regex-partial.h
     sampling.cpp
     sampling.h