stdio_dispatch: allow to select multiple stdio methods at the same time

[benpicco]

Contribution description

This implements the option to have multiple stdio methods active at the same time.
This can be useful to allow e.g. remote debugging while also retaining the possibility for local shell access.

To implement this, all stdin implementations are expected to write to a common stdin_isrpipe.

Two stdio providers have not been converted to the new interface yet, that means they can't be combined with a second stdio method:

• stdio_native: depends on cpu/native: use async read for stdio_read() #19002
• slipdev_stdio: depends on drivers/slipdev: make use of chunked ringbuffer #18066
• stdio_ethos: requires a similar patch as slipdev_stdio

If only a single stdio method is used, the function pointer/XFA based interface degrades into the traditional in-place implementations of stdio_init()/stdio_write() to avoid introducing any overhead in the common case.

Testing procedure

It is now possible to select multiple stdio implementations and use them all at the same time:

USEMODULE += stdio_cdc_acm
USEMODULE += stdio_uart
USEMODULE += stdio_udp
USEMODULE += stdio_telnet
USEMODULE += stdio_rtt

Issues/PRs references

fixes #13469

[benpicco]

This is now ready for review again.

[riot-ci]

Murdock results

✔️ PASSED

018b732 pkg/tinyusb/cdc_acm_stdio: only enable RX callback if stdin is active

Success	Failures	Total	Runtime
10016	0	10016	10m:18s

Artifacts

• Documentation preview