Tests

Bump third_party/imgui/repo from `3c435c0` to `45e7f78` #1175

Job	Run time
Test Suites - Darwin (no-ble-asan-clang)	1h 22m 50s
Test Suites - Darwin (no-ble-tsan-clang)	2h 2m 15s
Test Suites - Linux (no-ble-tsan-clang)	1h 1m 23s
REPL Tests - Darwin	0s
REPL Tests - Linux	1h 2m 26s
	5h 28m 54s

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