Allow multiple H2B converters in one HpInterface

Changes in this CL:
- Remove one argument from IMPLEMENT_HYBRID_META_INTERFACE and
  H2BConverter.
- Revise H2BConverter and HpInterface to allow multiple H2B converters
  in one HpInterface.
- Update the documentation.

Test: make cts -j123 && cts-tradefed run cts-dev -m \
CtsMediaTestCases --compatibility:module-arg \
CtsMediaTestCases:include-annotation:\
android.platform.test.annotations.RequiresDevice

Bug: 111902308

Change-Id: I3d4ec9b018134d3ad4d42c9ee5450c6c1228538d
2 files changed