fix: #353 "Vector2/3 reference not properly showing"

[soraphis]

fixes #353 and #357

The code before #289 has handled properties with custom-one-line-drawers (like Vector3) correctly, but did not handle custom structs - when collapsed - correctly.

this fix is the best of both worlds:

• Get the property height of the property if it would be expanded,
• then decided based upon whether or not it would occupy multiple lines.

this also fixes the broken StringReferences mentioned in (#357)

[jackalopy]

Please, pretty please, give this a little bit of attention. It should help us all <3

[AdamRamberg]

Good find! ⭐️ The code looks good to me! Pushed a smaller fix before the merge with a height adjustment of the popup button, which was covering the click area for underlying props when testing a struct.