Allow for per-chip flash logic and implement compression for esp32

[icewind1991]

Move the flash logic to a FlashTarget trait which can be customized per chip.

This is used to implement compression support for esp32 targets.

[jessebraham]

Awesome! Just out of curiosity which devices has this been tested on, if any?

[icewind1991]

it worked on my esp32 and c3

[MabezDev]

Before this PR:

cargo +esp-dev espflash --example blinky /dev/tty.usbserial-0001
    Finished dev [unoptimized + debuginfo] target(s) in 0.24s
[00:00:02] ########################################      27/27      segment 0x1000
[00:00:00] ########################################       3/3       segment 0x8000
[00:00:13] ########################################     139/139     segment 0x10000

With this PR:

cargo +esp-dev espflash --example blinky /dev/tty.usbserial-0001
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
Serial port: /dev/tty.usbserial-0001
Connecting...

[00:00:01] ########################################      16/16      segment 0x1000
[00:00:00] ########################################       1/1       segment 0x8000
[00:00:05] ########################################      49/49      segment 0x10000

Nice!

Edit: this is with an esp32.

[jessebraham]

Looks pretty good to me overall, thank you again. I did leave one comment, but it's not a huge deal.

For the ESP32-C3:

jesse@mbp ~/W/esp32c3-experiments master ✚1…1
λ cargo espflash /dev/cu.usbserial-14210                                                                                                                       2021-09-10 09:05:04
   Compiling esp32c3 v0.1.0 (/Users/jesse/Work/esp32c3-experiments)
    Finished dev [unoptimized + debuginfo] target(s) in 0.55s
Serial port: /dev/cu.usbserial-14210
Connecting...

[00:00:02] ########################################      20/20      segment 0x0
[00:00:00] ########################################       3/3       segment 0x8000
[00:00:02] ########################################      28/28      segment 0x10000
jesse@mbp ~/W/esp32c3-experiments master ✚1…1
λ cargo espflash /dev/cu.usbserial-14210                                                                                                                       2021-09-10 09:05:14
   Compiling esp32c3 v0.1.0 (/Users/jesse/Work/esp32c3-experiments)
    Finished dev [unoptimized + debuginfo] target(s) in 0.40s
Serial port: /dev/cu.usbserial-14210
Connecting...

[00:00:01] ########################################      12/12      segment 0x0
[00:00:00] ########################################       1/1       segment 0x8000
[00:00:01] ########################################      13/13      segment 0x10000

I'm just assuming it's still working for the ESP8266; unfortunately esp8266-hal needs updating so I am not able to build a binary with the most recent toolchain.