Adjust how compare_perf shows slowdown percentages #7139

Job	Run time
Windows (shared, x86_64, windows-2022)	5m 7s
Windows (static, x86_64, windows-2022)	5m 25s
Windows (amalgamation, x86_64, windows-2022)	7m 15s
Windows (shared, x86, windows-2022)	7m 20s
Clang Tidy	43s
Linux (gcc, shared)	1m 42s
Linux (gcc, amalgamation)	4m 32s
macOS (shared, xcode, macos-13)	3m 24s
Linux (gcc, static)	1m 36s
macOS (amalgamation, xcode, macos-13)	5m 1s
Analysis (coverage, gcc, ubuntu-24.04)	26m 10s
Linux (clang, shared)	1m 52s
Analysis (sanitizer, clang, ubuntu-24.04)	30m 0s
macOS (shared, xcode, macos-14)	1m 41s
Analysis (valgrind, clang, ubuntu-24.04)	49m 17s
macOS (amalgamation, xcode, macos-14)	3m 11s
Analysis (fuzzers, gcc, ubuntu-24.04)	15m 44s
Special (examples, gcc, ubuntu-24.04)	52s
Analysis (lint, gcc, ubuntu-24.04)	55s
Analysis (format, gcc, ubuntu-24.04)	37s
Cross (cross-i386, gcc, ubuntu-22.04)	3m 23s
Special (minimized, gcc, ubuntu-24.04)	22s
Analysis (limbo, gcc, ubuntu-24.04)	56s
Cross (cross-arm64, gcc, ubuntu-24.04)	12m 41s
Special (bsi, gcc, ubuntu-24.04)	1m 21s
Cross (cross-ppc64, gcc, ubuntu-24.04)	8m 1s
Special (docs, gcc, ubuntu-24.04)	1m 3s
Cross (cross-mips64, gcc, ubuntu-24.04)	9m 10s
Special (no_pcurves, gcc, ubuntu-24.04)	1m 27s
Cross (cross-android-arm64, clang, ubuntu-24.04)	1m 0s
Cross (static, gcc, windows-2022, make)	3m 49s
Cross (cross-ios-arm64, xcode, macos-13)	45s
Cross (cross-arm32-baremetal, gcc, ubuntu-24.04)	2m 10s
	3h 38m 32s

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