[VL] Initialize typeConvertor_ in VeloxToSubstraitPlanConvertor

[acvictor]

What changes are proposed in this pull request?

When running Gluten CPP tests with ASan/UBSan I see the following failure in velox_plan_conversion_test

[----------] 3 tests from SubstraitExtensionCollectorTest
  ...
I20260302 13:05:13.832439 18017 Task.cpp:2413] Terminating task test_cursor_3 with state Finished after running for 1ms
/mnt/vss/_work/1/s/Gluten/cpp/velox/substrait/VeloxToSubstraitPlan.cc:200:83: runtime error: member call on null pointer of type 'struct element_type'
    #0 0x155516780544 in gluten::VeloxToSubstraitPlanConvertor::toSubstrait(google::protobuf::Arena&, std::shared_ptr<facebook::velox::core::ValuesNode const> const&, substrait::ReadRel*) (/mnt/vss/_work/1/s/Gluten/cpp/build/releases/libvelox.so+0x24d80544) (BuildId: 3823968b38694acf997dceea565932e47a84025b)
    #1 0x155516787ff2 in gluten::VeloxToSubstraitPlanConvertor::toSubstrait(google::protobuf::Arena&, std::shared_ptr<facebook::velox::core::PlanNode const> const&, substrait::Rel*) (/mnt/vss/_work/1/s/Gluten/cpp/build/releases/libvelox.so+0x24d87ff2) (BuildId: 3823968b38694acf997dceea565932e47a84025b)
    #2 0x15551678b61f in gluten::VeloxToSubstraitPlanConvertor::toSubstrait(google::protobuf::Arena&, std::shared_ptr<facebook::velox::core::ProjectNode const> const&, substrait::ProjectRel*) (/mnt/vss/_work/1/s/Gluten/cpp/build/releases/libvelox.so+0x24d8b61f) (BuildId: 3823968b38694acf997dceea565932e47a84025b)
    #3 0x155516788760 in gluten::VeloxToSubstraitPlanConvertor::toSubstrait(google::protobuf::Arena&, std::shared_ptr<facebook::velox::core::PlanNode const> const&, substrait::Rel*) (/mnt/vss/_work/1/s/Gluten/cpp/build/releases/libvelox.so+0x24d88760) (BuildId: 3823968b38694acf997dceea565932e47a84025b)
    #4 0x15551678a118 in gluten::VeloxToSubstraitPlanConvertor::toSubstrait(google::protobuf::Arena&, std::shared_ptr<facebook::velox::core::PlanNode const> const&) (/mnt/vss/_work/1/s/Gluten/cpp/build/releases/libvelox.so+0x24d8a118) (BuildId: 3823968b38694acf997dceea565932e47a84025b)
    #5 0x5555620a121b in gluten::VeloxSubstraitRoundTripTest::assertPlanConversion(std::shared_ptr<facebook::velox::core::PlanNode const> const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcb4d21b) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #6 0x55556201ff8e in gluten::VeloxSubstraitRoundTripTest_project_Test::TestBody() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcacbf8e) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #7 0x555562105acc in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcbb1acc) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #8 0x5555620f4f0d in testing::Test::Run() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcba0f0d) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #9 0x5555620f50c4 in testing::TestInfo::Run() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcba10c4) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #10 0x5555620f51e4 in testing::TestSuite::Run() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcba11e4) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #11 0x5555620fcf2b in testing::internal::UnitTestImpl::RunAllTests() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcba8f2b) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #12 0x5555620f53ac in testing::UnitTest::Run() (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xcba13ac) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #13 0x555561d800c6 in main (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xc82c0c6) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)
    #14 0x1554ec027efa in __libc_start_call_main (/usr/lib/libc.so.6+0x27efa) (BuildId: 770b2da56f3278b92bc9ac4649f450a417ace260)
    #15 0x1554ec027fba in __libc_start_main (/usr/lib/libc.so.6+0x27fba) (BuildId: 770b2da56f3278b92bc9ac4649f450a417ace260)
    #16 0x555561da1514 in _start (/mnt/vss/_work/1/s/Gluten/cpp/build/velox/tests/velox_plan_conversion_test+0xc84d514) (BuildId: 3161011723acf3e0b9f071279f41d6ce7480fd14)

  *** UBSAN ERROR: velox_plan_conversion_test ***
42:/mnt/vss/_work/1/s/Gluten/cpp/velox/substrait/VeloxToSubstraitPlan.cc:200:83: runtime error: member call on null pointer of type 'struct element_type'

This is because typeConvertor_ is declared but never default initialized.

How was this patch tested?

Existing UTs

Was this patch authored or co-authored using generative AI tooling?

No

[acvictor]

@rui-mo can you please review this PR? Thanks in advance!

[rui-mo]

Thanks.