add hard reset to rfc2217 server (ESPTOOL-760)

[20162026]

add hard reset functionality to rfc2217 server and modify bootloader reset to trigger on DTR_ON instead of RTS_ON. This modification allows to use a rfc2217 server with idf_monitor and other compatible serial monitoring tools.
I'm not a python or rfc2217 expert and was assuming the default reset sequence, so there could be some issues with custom sequences.

This change fixes the following bug(s):

#892

I have tested this change with the following hardware & software combinations:

I have tested esp_rfc2217_server.py on windows10 and Ubuntu 22.04.2 LTS using custom esp32-wroom-32 board with the usual automatic bootloader circuit.

I have run the esptool.py automated integration tests with this change and the above hardware:

NO TESTING

[github-actions]

	Messages
📖	Good Job! All checks are passing!

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👋 Welcome 20162026, thank you for your first contribution to espressif/esptool project!

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[radimkarnis]

Hi @20162026,
thank you for your contribution! This is a very welcome addition.

I have synced the PR to our internal queue and will be testing the change soon. After a first look, the code LGTM!

I would like to ask you to do some stylistic changes:

1. The flake8 linter is failing, please see the failing GH Actions checks below.
2. Please change the commit message according to the conventional commits standard. Something like feat(rfc2217_server): Add hard reset sequence could work.

Thank you!

[20162026]

hi @radimkarnis,
stylistic changes are done.

[radimkarnis]

@20162026 thank you!
Sorry to bother, but there is still a small change to make reported by the black formater.
Sorry for this pedantic styling, esptool follows a certain code style and the commits cannot be merged until the code complies. I would make the changes myself, but then you'd lose a GitHub contributor credit, because the commit would be altered by me.

[20162026]

@radimkarnis fixed.
Im not quite sure why black did not catch error when i was commiting localy as I did use the precommit hook, however now I ran linters manually and it should be ok

[dobairoland]

@radimkarnis I've noticed that the link to the project contribution guide is invalid in #929 (comment).

[dobairoland]

Hi @20162026. Thank you for your contribution. We will be happy to receive any feedback regarding the contribution process. Maybe we can something improve in our guides?

[radimkarnis]

@20162026 thank you again! Now merged to master. This will propagate to ESP-IDF for use with other tools with the next esptool release.