Implement webnn-baseline and WPT for operations needed for well-known transformers

[huningxin]

Opening this issue to track the implementation status of webnn-baseline and WPT for operations needed for well-known transformers.

Ops	Baseline	WPT tests
equal, lesser, greater, greaterOrEqual, lesserOrEqual, not	√	pr
where	pr	WIP
copy	√	pr
reciprocal	√	pr
sqrt	√	pr
erf
expand	pr	WIP
gather
layerNormalization
reduceArgMin, reduceArgMax
cast
triangular

/cc @inexorabletash @BruceDai @wchao1115 @fdwr @anssiko

[BruceDai]

Updated

Ops	Baseline	WPT tests
equal, lesser, greater, greaterOrEqual, lesserOrEqual, not(logicalNot)	√	√
where	√	√
copy(identity)	√	√
reciprocal	√	√
sqrt	√	√
erf	√	√
expand	√	√
gather	√	√
layerNormalization	√	√
argMin, argMax	√	√
cast	√	√
triangular	√	pr
constant(fillSequence)	√	pr
reshape(squeeze,unsqueeze,flatten)	√	√

[anssiko]

WPT for constant fillSequence web-platform-tests/wpt#43801 and triangular web-platform-tests/wpt#43794 merged.