extmod/modussl_mbedtls: Add closenotify() method

[dimkr]

Sending a FIN without a close_notify alert breaks some protocols: in my case, Gemini. (I'm running a Gemini server on a Pico W.)

This can block or slow down existing code that expects .close() not to do this, so it's a separate method.

[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 

[codecov-commenter]

Codecov Report

Merging #10783 (6c7c0a1) into master (4598b89) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

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@@            Coverage Diff             @@
##           master   #10783      +/-   ##
==========================================
- Coverage   98.50%   98.48%   -0.02%     
==========================================
  Files         155      155              
  Lines       20540    20544       +4     
==========================================
  Hits        20232    20232              
- Misses        308      312       +4     

Impacted Files	Coverage Δ
extmod/modussl_mbedtls.c	88.05% <0.00%> (-1.79%)	⬇️

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[dpgeorge]

Thanks for the contribution.

This is not compatible with CPython, which doesn't have this closenotify() method. We need to find a solution that is compatible with CPython.

If you were implementing a Gemini server to run under CPython, how would it work?

[dimkr]

I can move this to close(), requiring a CLOSING state before CLOSED. That would make close() a potentially blocking call.

EDIT: looked at cpython, close_notify belongs in shutdown().

[projectgus]

This is an automated heads-up that we've just merged a Pull Request
that removes the STATIC macro from MicroPython's C API.

See #13763

A search suggests this PR might apply the STATIC macro to some C code. If it
does, then next time you rebase the PR (or merge from master) then you should
please replace all the STATIC keywords with static.

Although this is an automated message, feel free to @-reply to me directly if
you have any questions about this.