Add print in BacktraceFmt #616

Job	Run time
iOS (aarch64-apple-ios, iphoneos)	1m 24s
iOS (x86_64-apple-ios, iphonesimulator)	54s
Docker (aarch64-unknown-linux-gnu)	56s
Docker (arm-unknown-linux-gnueabihf)	1m 5s
Docker (armv7-unknown-linux-gnueabihf)	1m 9s
Docker (i586-unknown-linux-gnu)	51s
Docker (i686-unknown-linux-gnu)	55s
Docker (powerpc64-unknown-linux-gnu)	1m 4s
Docker (s390x-unknown-linux-gnu)	1m 6s
Docker (x86_64-pc-windows-gnu)	51s
Docker (x86_64-unknown-linux-gnu)	46s
Docker (x86_64-unknown-linux-musl)	48s
Docker (arm-linux-androideabi)	3m 10s
Docker (armv7-linux-androideabi)	3m 29s
Docker (aarch64-linux-android)	3m 22s
Docker (i686-linux-android)	3m 17s
Docker (x86_64-linux-android)	2m 57s
Rustfmt	7s
Test (ubuntu-20.04, stable)	2m 56s
Test (ubuntu-20.04, beta)	3m 24s
Test (ubuntu-20.04, nightly)	3m 37s
Test (macos-latest, stable)	4m 21s
Test (macos-latest, nightly)	4m 21s
Test (windows-latest, stable-x86_64-msvc)	4m 11s
Test (windows-latest, stable-i686-msvc)	3m 59s
Test (windows-latest, stable-x86_64-gnu)	4m 26s
Windows AArch64	2m 1s
Build Targets (wasm32-unknown-unknown)	26s
Build Targets (wasm32-wasi)	28s
Build Targets (x86_64-unknown-fuchsia)	25s
Build Targets (x86_64-fortanix-unknown-sgx)	31s
Build Targets (x86_64-unknown-illumos)	26s
Miri	3m 36s
MSRV	2m 18s
	1h 9m 37s

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