Handle new Rocq 9.2 warnings

[proux01]

• Added changelog.
• Added / updated documentation.

• Opened overlay pull requests.

[SkySkimmer]

BTW in the log you will see a few warnings like

File "./btauto/Algebra.v", line 394, characters 0-54:
Warning:
Autogenerated "rew" scheme for null.
Use "Scheme Rewriting for null" to explicitly generate it.
This will become an error in the future.
[missing-scheme,deprecated-since-9.2,deprecated,default]

stdlib/theories/btauto/Algebra.v

Line 394 in b9f913a

case_decide; simpl; try_rewrite; [ring_simplify|ring].

This is from a try_rewrite, and the rewrite does nothing so if the warning is turned into an error the proof still succeeds (but silently).

[proux01]

Thanks for pointing it but why does neither Set Warnings "+default" nor Set Warnings "+missing-scheme". turn it as error? (it seems to silence the warning here, that effect being seamingly specific to that warning)
[my bad, thanks for the explanation]

[proux01]

Noted missing-scheme as requiring handling when requiring Rocq >= 9.2 (so that it can now be turned as error by default).

[SkySkimmer]

It does turn it as error, but try ignores the error.

[proux01]

Yes, sorry, took me some time to understand (apparently, I need a break)