Bump bundled opentelemetry-proto to v1.10.0 and regenerate (#5223)

Update PROTO_REPO_BRANCH_OR_COMMIT in scripts/proto_codegen.sh from
v1.9.0 to v1.10.0, regenerate the generated *_pb2.py / *_pb2.pyi files,
and update the opentelemetry-proto README version references to match.

The motivation is the profiles v1development proto: in the v1.9.0 pin
the Sample message carried outdated field numbers
(stack_index=1, values=2, attribute_indices=3, link_index=4,
timestamps_unix_nano=5). v1.10.0 (2026-03-09) renumbers it to
stack_index=1, attribute_indices=2, link_index=3, values=4,
timestamps_unix_nano=5, which the regenerated descriptors now reflect.

The bump also pulls in unrelated proto changes between v1.9.0 and
v1.10.0: common v1 gains AnyValue.string_value_strindex and
KeyValue.key_strindex fields (development, profiling-oriented), and a
SeverityNumber doc-comment was dropped in logs v1.

Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>