Removed deprecated 3.x APIs in core-frontend except rpcInterface, scheduleScriptReference and getThumbnail

[williamzqr1]

PR for removing the deprecated 3.x APIs in core-frontend. Most of the APIs that are deprecated in 3.x have been removed.
There are three of the APIs that have not been removed yet.

1. rpcInterface: https://github.com/iTwin/itwinjs-backlog/issues/1374
2. scheduleScriptReference: https://github.com/iTwin/itwinjs-backlog/issues/1375
3. getThumbnail: https://github.com/iTwin/itwinjs-backlog/issues/1376

I will create sub issues for them and link the issues in this PR.

[williamzqr1]

@pmconne
For scheduleScriptReference, I was confused by the usage of sourceId from scheduleScriptReference. Most of the places that used sourceId cannot be simply replaced by scheduleScript. And removing the usage of sourceId would affect the functionality of the code. For example in here

For rpcInterface, I will add a separate issue for that one

[pmconne]

For scheduleScriptReference

Reserve it for a separate PR and file an issue where we can discuss.

[mergify]

This pull request is now in conflicts. Could you fix it @williamzqr1? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[williamzqr1]

Separate issue for rpcInterfaces: https://github.com/iTwin/itwinjs-backlog/issues/1374

[dassaf4]

core-geometry.api.md changes are already on main due to #7588, so when you update branch, those should disappear.

[anmolshres98]

I see that multiple files have only whitespace changes. I figure that this is because you edited those files initially when attempting make all changes in this branch but reverted them to break them out into separate PRs. Ideally you would want to revert all changes that is only whitepsace changes too but I don't think that should hold up this PR so imo fine for now. Just something to look out for next time :)