implement transaction context

[alex-dukhno]

Link with #574

Description

introduced TransactionContext to execute multiple queries per transactions

[coveralls]

Pull Request Test Coverage Report for Build 809578887

• 1036 of 1696 (61.08%) changed or added relevant lines in 12 files are covered.
• 18 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+1.8%) to 66.556%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
node_engine/src/lib.rs	0	1	0.0%
sql_engine/data_definition/execution_plan/src/lib.rs	6	7	85.71%
sql_engine/query_planner/src/lib.rs	43	46	93.48%
sql_engine/data_manipulation/query_plan/src/lib.rs	17	21	80.95%
node_engine/src/query_engine/mod.rs	73	81	90.12%
sql_engine/query_analyzer/src/lib.rs	122	132	92.42%
sql_engine/definition_planner/src/lib.rs	59	73	80.82%
storage/src/lib.rs	48	72	66.67%
sql_engine/catalog/src/lib.rs	199	324	61.42%
node_engine/src/query_engine_old/mod.rs	466	936	49.79%

Files with Coverage Reduction	New Missed Lines	%
sql_engine/query_analyzer/src/lib.rs	1	91.97%
sql_engine/definition_planner/src/lib.rs	17	69.28%

Totals
Change from base Build 801891097:	1.8%
Covered Lines:	3005
Relevant Lines:	4515

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💛 - Coveralls