fix: Short-circuit File and Date constructor access in isObject

[Hsifnus]

Reasons for making this change

This change refactors isObject to significantly reduce the frequency of accesses to File and Date by short-circuiting the function with several simple checks prior to running instanceof checks involving the two native classes. The motivation for making this change is explained within the issue this pull request fixes.

fixes #4409

Prior isObject logic

• If File is defined and the value is an instance of File, return false
• If Date is defined and the value is an instance of Date, return false
• Return true if and only if the value is a non-null, non-array object

New isObject logic

• If value is null or a non-object, return false
• If value has a lastModified number property and File is defined and the value is an instance of File, return false
• If value has a getMonth method and Date is defined and the value is an instance of Date, return false
• Return true if the value if an only if the value is a non-array object

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npx nx run-many --target=build --exclude=@rjsf/docs && npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature