[LLVM][RUNTIME] Make ORCJIT LLVM executor the default one

[cbalint13]

This PR propose to make ORCJIT the default LLVM runtime executor (engine).

Notes

• Currently ORCJIT is a optional executor under llvm -jit=orcjit flag, introduced here.
• Targets like RISCV, and possible others too, will not work on MCJIT see some discussions here .
• As a live example, similar project Halide already use ORCJIT completley replacing the old MCJIT engine.

TVM disscussions and recent issues on the subject:

• https://discuss.tvm.apache.org/t/run-tvm-software-stack-on-risc-v/17683/4
• [Bug] Unsupported CPU on SpacemiT K1 Otca-core X60(RV64GCVB),RVA22, #17508

Since ORCJIT was poorly exposed within TVM until now (being optional) any rising issues will need attention.

[cbalint13]

This is ready for review.
Cc: @masahi , @vinx13, @tqchen , @ekalda , @lhutton1 , @quic-sanirudh , @kparzysz-quic , @Lunderberg
Cc: @katebern-grovety , @PhilippvK, @JieGH

[tqchen]

@cbalint13 can you dig a bit into windows issue? seems related to a missing symbol

[cbalint13]

@cbalint13 can you dig a bit into windows issue? seems related to a missing symbol

@tqchen , Yes I am on it, it will take a little bit of time.

[cbalint13]

@tqchen ,

• The MSWIN __ImageBase issue is fixed using COFF workaround flags via explicit JIT linkage pass.
• For track of record, the reference LLVM example was used here, where mentioned flags are showcased.

If this goes to main will help track & tackle issues as they arise, I hope for the best that there will be none at all.

[cbalint13]

@tvm-bot rerun