regen(pb2): messages_solana with the pinned image, for the KKSOLSW1 tags

Regenerated with docker_build_pb.sh's toolchain -- kktech/firmware:v8, which
carries protoc 3.5.1 -- so the output is the same old-style generated code as
every other *_pb2.py in this package:

    DESCRIPTOR = _descriptor.FileDescriptor(...)

That style is not incidental. The CI test container is Alpine 3.8 / Python
3.6.9, and its protobuf runtime cannot load modern descriptor_pool generated
code; a modern-protoc regeneration of this one file took down
python-integration-tests, and generate-test-report with it, on every alpha run
until it was reverted.

Adds the SolanaSignTx lut_account / lut_signature / lut_signer_key_id fields
(tags 5-7) so the KKSOLSW1 tests can construct the message.

Verified against the emulator: KKSOLSW1 suite 4/4, full pyk 632 passed /
25 skipped / 0 failed.

Author: BitHighlander