v0.8.4-dev

• adds flywoof411rx target
• fix objcopy for building on windows
• filters: use auto-detected looptime for period
• enable lto
• crsf: send cell voltage
• adds aikon_f7 target
• adds hifionrc_f722 target
• adds foxeerf745_aio target
• H7 support for H743
• rework all spi devices to use spi-txn
• various improvements to spi-txn
• bmi270: change hardware lpf to use approximately the same cut-off as mpu6000
• blackbox: write entries tightly packed to flash, increasing recording time
• add halfduplex serial pass-through support
• add mspv2 support
• add msp serial pass-through support