Remove _fullInput and other dead transforms code

[emilykl]

Addresses #7250

• The trace._fullInput field existed solely for keeping track of the original input trace after applying defaults but before applying transforms
• Now that the transforms feature has been fully removed (see Drop transforms from the API #7240, Remove transforms from bundles #7254), trace._fullInput is the same as trace
• This PR changes all references to trace._fullInput to simply trace, and adjusts logic accordingly
• Also removes trace._indexToPoints which was likewise only used for transforms
• Removes some other dead transforms code which was unused but still in codebase
• Finally, updates or removes tests which referenced trace._fullInput or transforms

This PR should have zero user-facing impact.

[camdecoster]

Looks good! Two things:

• Could you add a draftlog? Since this removes the deprecated code, it would be good to note that.
• Could you do a sweep for comments that mention transforms or _fullData?

[emilykl]

• Could you add a draftlog? Since this removes the deprecated code, it would be good to note that.

Sure, I can add a draftlog, it could help with debugging later, so not a bad idea. But the removed code was already inaccessible so I don't expect any user-facing changes.

• Could you do a sweep for comments that mention transforms or _fullData _fullInput?

Good idea! 0 matches for fullInput, but a bunch of matches for transforms. I'll look at each of those more closely and modify or remove.