Use single WASM interface for parallel read-only trx execution

[linh2931]

This is one of work items identified in https://github.com/eosnetworkfoundation/product/issues/149 for https://github.com/eosnetworkfoundation/product/pull/161.

In current parallel EOS-VM and EOS-VM-JIT execution, each thread uses a separate WASM interface. This causes several issues:

• It makes common module cache required for sharing the same compiled WASM module hard to implement.
• The multiple WASM interfaces and associated thread data make code complicated and hard to reason.
• It is not consistent with EOS-VM-OC where only one WASM interface is required.

Single WASM interface is to be used.

[bhazzard]

I need to simplify the related product initiatives into one.

[linh2931]

PRs:

Leap -- https://github.com/AntelopeIO/leap/pull/1549 EOS VM -- https://github.com/AntelopeIO/eos-vm/pull/20