Simplify connection module

[coveralls]

Pull Request Test Coverage Report for Build 767907076

• 108 of 158 (68.35%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.7%) to 64.207%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
postgre_sql/wire_protocol/src/lib.rs	0	5	0.0%
postgre_sql/wire_protocol/src/connection/mod.rs	108	125	86.4%
node_engine/src/lib.rs	0	28	0.0%
<!--	Total:	108	158	68.35%	-->

Totals
Change from base Build 760974259:	0.7%
Covered Lines:	2628
Relevant Lines:	4093

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💛 - Coveralls