WebView Tracing API: remove LARGE_BUFFER, make RECORD_CONTINUOUSLY the default mode

This patch:
- remove the RECORD_UNTIL_FULL_LARGE_BUFFER tracing option, because
  this does not appear really useful in the production setting as
  the buffer size limit exceeds the device memory and can grow
  uncontrollably large.
- make RECORD_CONTINUOUSLY the default mode for tracing, to make
  sure the least memory is used by default (typically 4x less than the
  previous default RECORD_UNTIL_FULL).
- add some missing IntDef values (to make them match with the constants)

BUG: 63750258
Test: CTS

Change-Id: Ib3698273dee776ebc7a8388fc1bd8c80255e3b63