Initial conversion work to indexed metadata

src/core/ext/lb_policy/grpclb/grpclb.c

src/core/ext/load_reporting/load_reporting_filter.c

src/core/lib/channel/compress_filter.c

src/core/lib/channel/http_client_filter.c

src/core/lib/channel/http_server_filter.c

src/core/lib/iomgr/error.c

src/core/lib/iomgr/error.h

src/core/lib/security/transport/client_auth_filter.c

src/core/lib/security/transport/server_auth_filter.c

src/core/lib/surface/call.c

src/core/lib/surface/server.c

src/core/lib/transport/metadata_batch.c

src/core/lib/transport/metadata_batch.h

src/core/lib/transport/static_metadata.c

src/core/lib/transport/static_metadata.h

test/core/end2end/fuzzers/hpack.dictionary

tools/codegen/core/gen_static_metadata.py