stdexec: update to latest

* Add a .clang-format-ignore for the stdexec and stop running
clang-format on it. This makes it identical to the stdexec
source.

* Add a warning exception for

stdexec: update to latest

* Add a .clang-format-ignore for the stdexec and stop running
clang-format on it. This makes it identical to the stdexec
source.

* Add a warning exception for -Wempty-body.

* Remove a requirement constraint on the spawn function. The
sender_of constraint can no longer analyze certain stdexec
generated classes and appears to be deprecated. In the future
I may be able to figure out a newer constraint for better
diagnostics, but this is only for diagnostic purposes.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ic29b7052b1e3a1818fbbfbd42aefe2990f4295c7

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