Logical OR, AND, and NOT variants

Context

This proposal is based on typst/typst#4939. See the pull request description and discussion thread for additional context and concerns.

Add the symbol variants from the following table under sym.

Character	Name
⩞ LOGICAL AND WITH DOUBLE OVERBAR (Binary)	`eq.and`
⩢ LOGICAL OR WITH DOUBLE OVERBAR (Binary)	`eq.or`
⫬ DOUBLE STROKE NOT SIGN (Relation)	`not.double`
⌐ REVERSED NOT SIGN (Normal)	`not.rev`
⫭ REVERSED DOUBLE STROKE NOT SIGN (Relation)	`not.rev.double`
⌙ TURNED NOT SIGN (Normal)	`not.inv`
⩠ LOGICAL AND WITH DOUBLE UNDERBAR	`and.eq`
⩙ LOGICAL OR OVERLAPPING LOGICAL AND (Relation)	`and.or` and `or.and`
⩘ SLOPING LARGE AND (Binary)	`and.sloped` (maybe `and.slope`)
⩚ LOGICAL AND WITH MIDDLE STEM (Binary)	`and.stem`
⩜ LOGICAL AND WITH HORIZONTAL DASH (Binary)	`and.struck`
⩕ TWO INTERSECTING LOGICAL AND (Binary)	`and.twice`
⨇ TWO LOGICAL AND OPERATOR (Large)	`and.twice.big`
⩣ LOGICAL OR WITH DOUBLE UNDERBAR (Binary)	`or.eq`
⩗ SLOPING LARGE OR (Binary)	`or.sloped` (maybe `or.slope`)
⩛ LOGICAL OR WITH MIDDLE STEM (Binary)	`or.stem`
⩝ LOGICAL OR WITH HORIZONTAL DASH (Binary)	`or.struck`
⩖ TWO INTERSECTING LOGICAL OR (Binary)	`or.twice`
⨈ TWO LOGICAL OR OPERATOR (Large)	`or.twice.big`

In light of the recent PR I took another look at this and I now have two concerns:

.slope vs. .sloped: Is this meaningfully different from the already existing .slant/.slanted?
.twice: We already have a {lt,gt}.double vs. {lt,gt}.double.nested distinction. Shouldn't this then just be {and,or}.double and the nested one be renamed to {and,or}.double.nested? Tho all the existing cases of .double for set and logical operators seem to be nested already, so perhaps we should add .nested to those as well?