Use single WASM interface for parallel read-only trx execution

[linh2931]

This is one of work items identified in eosnetworkfoundation/product#149 for eosnetworkfoundation/product#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 -- #1549
EOS VM -- AntelopeIO/eos-vm#20