feat: Minimize number of connections used by parallel reader #237

Job	Run time
Run TPC-DS queries with SF=1	57m 57s
${{ matrix.test-target }} test on ${{ matrix.os }} with java ${{ matrix.java_version }}	0s
rust test on macos-aarch64 with java 8	3m 58s
rust test on ubuntu-latest with java 8	5m 16s
java test on macos-aarch64 with java 8	1h 29m 42s
java test on ubuntu-latest with java 8	2h 6m 50s
rust test on macos-aarch64 with java 17	4m 25s
rust test on ubuntu-latest with java 17	6m 8s
java test on macos-aarch64 with java 17	1h 39m 42s
java test on ubuntu-latest with java 17	1h 26m 46s
	8h 0m 44s

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