Remove ignore: deprecated_member_use and adopt nonlinear text scaling

[LongCatIsLooong]

Existing issue?

• I checked the existing issues

What happened?

2 ignore: deprecated_member_use were added in #982 to temporarily address textScaleFactor deprecation. They should be removed and the codebase should switch to using TextScaler instead.

Currently some UI components are scaled by text scale factor (an example:

gallery/lib/studies/crane/backdrop.dart

Lines 242 to 243 in 18f1e8e

	20 * textScaleFactor / 2
	: 175 + 140 * textScaleFactor / 2,

) which may not work as well with nonlinear text scaling, as the text scaling curve isn't designed to scale non-textual contents (e.g. it may not work well when the dimension is not in the typical font size range).

Relevant log output

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