inputflinger fuzzers: Remove FuzzContainer

As discussed on the touchpad fuzzer CL [0], FuzzContainer was hiding
quite a bit of internal state and making fuzzers harder to understand.
Its constructor appeared to be deduplicating code, but looking more
closely, it wasn't really helping that much, especially for the most
common cases. Replace it with a few static methods, making it clearer
how state is being changed in the fuzzers.

[0] Change ID Ic22ac0f29d433fdf3c17331df620a39937ebd7eb

Bug: 245989146
Test: build and briefly run all modified fuzzers
      $ SANITIZE_TARGET=hwaddress make ${FUZZER_NAME}
      $ cd $ANDROID_PRODUCT_OUT
      $ adb root
      $ adb sync data
      $ adb shell /data/fuzz/$(get_build_var TARGET_ARCH)/${FUZZER_NAME}/${FUZZER_NAME}

Change-Id: I6e28b1f5ec62dc2d084173c1eb461c4bb699678b