[debug] add a new channel events mechanism for debugging

[ctl] allow to specific instance name for instance commands in $CW_INSTANCE Closes #17253994

[cubicweb/utils] add QueryCache.__contains__() to improve dict-like behavior. Closes #255426

[migrations/pdb] add to every failing migration operation a "p(db)" option Instead, the migration command will just crash without offering the possibility of the user to debug or continue the migration. Closes #17219772

[pyramid/ctl] add a new option to activate the debugtoolbar (-t) While this toolbar isn't yet very integrated with CW, it integrates an inline debugging shell like werkzeug for flask or django_extensions which greatly helps debugging on exception. It can already be manually activated by writting "pyramid.includes = pyramid_debugtoolbar" but it's hidden somewhere in the documentation and not very accessible and annoying to do. Closes #17219765

[changelog] add missing information to the 3.27 changelog

Merge 3.26

[debug] add ALL possibility to --dbglevel

[ux] display instance name in suggested upgrade command

[migration/pdb] display traceback instead of only the exception for easier debugging Closes #17219820

[migration/pdb] add option to use pdb.post_mortem if traceback is provided Post mortem is a mode where the pdb shell is opened **where** the exception as occured instead at the breakpoint for set_trace. This is way more useful for debugging for the user because is will have the full context of the error. Closes #17219827

[migration/shell] select ipdb if present on (d)ebug mode Closes #17219833