operation_history_object::virtual_op numbering may be discontinuous (possibly with holes)

[abitmore]

Bug Description

In database::push_applied_operation(), after _current_virtual_op is assigned to virtual_op of the newly created operation_history_object, _current_virtual_op++ is called:

bitshares-core/libraries/chain/db_block.cpp

Lines 535 to 544 in f812666

	uint32_t database::push_applied_operation( const operation& op )
	{
	_applied_ops.emplace_back(op);
	operation_history_object& oh = *(_applied_ops.back());
	oh.block_num = _current_block_num;
	oh.trx_in_block = _current_trx_in_block;
	oh.op_in_trx = _current_op_in_trx;
	oh.virtual_op = _current_virtual_op++;
	return _applied_ops.size() - 1;
	}

If the operation being pushed is in a proposal, after it is added to _applied_ops, it may be removed later if the proposal fails, but _current_virtual_op is not updated back:

bitshares-core/libraries/chain/db_block.cpp

Lines 361 to 364 in f812666

	else
	{
	_applied_ops.resize( old_applied_ops_size );
	}

I'm not sure if it is worth fixing.

#1675 is related.

Impacts
Describe which portion(s) of BitShares Core may be impacted by this bug. Please tick at least one box.

• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)

Host Environment
Please provide details about the host environment. Much of this information can be found running: witness_node --version.

• BitShares Version: 6.0.2

CORE TEAM TASK LIST

• Evaluate / Prioritize Bug Report
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation