Add support for `WHERE` clause in `copy_to` methods #478

Job	Run time
test-postgres (9.5)	4m 20s
test-postgres (9.6)	3m 15s
test-postgres (10)	3m 57s
test-postgres (11)	3m 24s
test-postgres (12)	3m 50s
test-platforms (3.8, ubuntu-latest, asyncio)	2m 46s
test-postgres (13)	3m 43s
test-platforms (3.8, ubuntu-latest, uvloop)	2m 16s
test-postgres (14)	3m 7s
test-platforms (3.8, macos-latest, asyncio)	3m 4s
test-postgres (15)	3m 3s
test-platforms (3.8, macos-latest, uvloop)	3m 10s
test-postgres (16)	3m 2s
test-platforms (3.8, windows-latest, asyncio)	7m 28s
test-platforms (3.9, ubuntu-latest, asyncio)	2m 36s
test-platforms (3.9, ubuntu-latest, uvloop)	2m 43s
test-platforms (3.9, macos-latest, asyncio)	5m 33s
test-platforms (3.9, macos-latest, uvloop)	4m 0s
test-platforms (3.9, windows-latest, asyncio)	6m 45s
test-platforms (3.10, ubuntu-latest, asyncio)	2m 19s
test-platforms (3.10, ubuntu-latest, uvloop)	2m 8s
test-platforms (3.10, macos-latest, asyncio)	3m 3s
test-platforms (3.10, macos-latest, uvloop)	5m 34s
test-platforms (3.10, windows-latest, asyncio)	6m 53s
test-platforms (3.11, ubuntu-latest, asyncio)	2m 22s
test-platforms (3.11, ubuntu-latest, uvloop)	2m 27s
test-platforms (3.11, macos-latest, asyncio)	5m 17s
test-platforms (3.11, macos-latest, uvloop)	4m 19s
test-platforms (3.11, windows-latest, asyncio)	6m 18s
test-platforms (3.12, ubuntu-latest, asyncio)	2m 34s
test-platforms (3.12, macos-latest, asyncio)	3m 33s
test-platforms (3.12, windows-latest, asyncio)	7m 29s
Regression Tests	1s
	2h 6m 19s

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