feat(c/driver/postgresql): customize numeric conversion #2256

Job	Run time
clang-tidy	5m 51s
Common Libraries (Conda/macos-latest)	2m 57s
Common Libraries (Conda/ubuntu-latest)	2m 28s
C/C++ (Conda/macos-latest)	2m 31s
C/C++ (Conda/ubuntu-latest)	2m 46s
Go (No CGO) (macos-latest)	2m 32s
Go (No CGO) (ubuntu-latest)	1m 57s
Go (No CGO) (windows-latest)	4m 51s
Go (CGO) (Conda/${{ matrix.os }})	0s
Documentation ${{ matrix.python }} (Conda/${{ matrix.os }})	0s
Python ${{ matrix.python }} (Conda/${{ matrix.os }})	0s
GLib/Ruby (Conda/${{ matrix.os }})	0s
	25m 53s

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