ruby : Make context accept initial parameters, API to retrieve a segment and more...

ruby : Make context accept initial parameters, API to retrieve a segment and more (#2749)

* Fix type signature for Whisper.log_set

* Use cache file for model when offline

* Extract ruby_whisper_transcribe() into a file

* Extract Whisper::Error

* Use FileList for ext/*.{c,cpp,h}

* Extract Whisper::Segment

* Extract Whisper::Model

* Extract Whisper::Params

* Extract Whisper::Context

* Extract log_callback function

* Write base code in C rather than C++

* Use chdir instead of Dir.chdir in Rakefile

* Define alloc func for Whisper::Model

* Define Whisper::Params' calback and user data reader

* Add test for Whisper::Params.new with keyword arguments

* Make Whisper::Params.new accept keyword arguments

* Update type signatures

* Update README

* Update CLEAN targets

* Fix document comment for Whisper::Params#new_segment_callback=

* Use macro to define params

* Fix dependency of build task

* Set Whisper.finalize_log_callback visibility to private

* Make Whisper::Context#full and full_parallel return self

* Add test for Whisper::Context#full_get_segment

* Add Whisper::Context#full_get_segment

* Update signatures

* Update README

* Fix signature

* Resplace #initialize with .new in signature file [skip ci]

* Fix potential overflow