Fix signature matching for externals when abstract alias hides functi… #9002

Job	Run time
build-compiler (ubuntu-24.04, ocaml-variants.4.14.2+options,ocaml-option-static, linux-x64, x86_6...	3m 13s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	4m 4s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	6m 2s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	3m 0s
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	7m 1s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	8m 18s
pkg-pr-new	51s
api-docs	1m 31s
test-installation-pnpm (macos-15-intel)	31s
test-installation-pnpm (ubuntu-24.04)	16s
test-installation-pnpm (ubuntu-24.04-arm)	17s
test-installation-npm (macos-15)	21s
test-installation-pnpm (windows-2025)	43s
test-installation-pnpm (macos-15)	21s
test-integration-rewatch (windows-2025)	3m 10s
test-integration-rewatch (macos-15-intel)	2m 46s
test-integration-rewatch (ubuntu-24.04)	1m 15s
test-installation-npm (windows-2025)	1m 30s
test-installation-npm (macos-15-intel)	38s
test-installation-npm (ubuntu-24.04)	18s
test-installation-npm (ubuntu-24.04-arm)	26s
test-integration-rewatch (macos-15)	1m 24s
test-integration-rewatch (ubuntu-24.04-arm)	1m 9s
publish	-1s
	49m 4s

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