Supress excessive_precision when constants are overly precise

[teofr]

Suppress the excessive_precision lint when the literal is the initializer of a const item and overly precise (over 40 digits).
If an overly precise literal is used in a let initialization it produces a note suggesting the change.

changelog: [excessive_precision]: suppress the lint when const items are overly precise

Fixes #13855

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[teofr]

Suggested change

	| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	| ^^^

Ideally I would like this to only underline the let keyword, I couldn't find that span in the HIR node, any help or pointer is appreciated.