MediaCodecList: reload MediaCodecList instance after boot

Refactor the static member variables into a class, and check
boot status at getting the codec list objects, guarded behind
a flag.

Bug: 297922713
Test: presubmit
Flag: android.media.codec.in_process_sw_audio_codec_support
Change-Id: If75f15a6f94a5cc2fe0b036e50a7860713943964