convert: rework ftype heuristics (#18214)

convert: rework ftype heuristics (#18214)

* convert: rework ftype heuristics

Signed-off-by: Aaron Teo <redacted>
convert: fix type-check

Signed-off-by: Aaron Teo <redacted>
convert: bring back heuristics comment

Signed-off-by: Aaron Teo <redacted>
* convert: revert to using first tensor

Signed-off-by: Aaron Teo <redacted>
* convert: rework heuristics logic

Signed-off-by: Aaron Teo <redacted>
* convert: rm redundant float32 check

Co-authored-by: Sigbjørn Skjæret <redacted>
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Signed-off-by: Aaron Teo <redacted>
Co-authored-by: Sigbjørn Skjæret <redacted>