[Merged by Bors] - chore: namespace some IsSelfAdjoint lemmas

[j-loreaux]

Per this Zulip discussion we choose to namespace (and protect) a few lemmas about IsSelfAdjoint.

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[github-actions]

PR summary ac50c1f301

Import changes

No significant changes to the import graph

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Declarations diff

+ add_star_self
+ intCast
+ natCast
+ nnratCast
+ ofNat
+ one
+ ratCast
+ star_add_self
+ zero
- _root_.isSelfAdjoint_add_star_self
- _root_.isSelfAdjoint_intCast
- _root_.isSelfAdjoint_natCast
- _root_.isSelfAdjoint_nnratCast
- _root_.isSelfAdjoint_ofNat
- _root_.isSelfAdjoint_one
- _root_.isSelfAdjoint_ratCast
- _root_.isSelfAdjoint_star_add_self
- _root_.isSelfAdjoint_zero

You can run this locally as follows

## summary with just the declaration names:
./scripts/no_lost_declarations.sh short <optional_commit>

## more verbose report:
./scripts/no_lost_declarations.sh <optional_commit>

[kim-em]

bors merge

[mathlib-bors]

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[mathlib-bors]

Pull request successfully merged into master.

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