Use EventrwflagsDetails in fmt::Debug impl for wasi::Event #465

Job	Run time
TestWakerPipe	35s
TestPoll	26s
CheckTargets	1m 27s
Clippy	7s
Check (aarch64-apple-ios)	30s
Docs	19s
Check (aarch64-apple-tvos)	29s
Check (aarch64-unknown-openbsd)	29s
MinimalVersions (ubuntu-latest)	16s
MSRV (ubuntu-latest)	13s
Check (arm64_32-apple-watchos)	36s
Nightly	15s
MinimalVersions (macos-latest)	17s
Check (armv7-sony-vita-newlibeabihf)	31s
MSRV (macos-latest)	17s
MinimalVersions (windows-latest)	44s
MSRV (windows-latest)	37s
Check (sparcv9-sun-solaris)	32s
Rustfmt	6s
Check (x86_64-pc-solaris)	31s
Sanitizer (address)	37s
Check (x86_64-unknown-dragonfly)	31s
Test (ubuntu-latest)	45s
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Check (x86_64-unknown-openbsd)	32s
Test (macos-latest)	42s
Sanitizer (memory)	41s
Test (windows-latest)	2m 6s
Sanitizer (thread)	34s
Passed	0s
	16m 20s

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