[Code health] Cleanup `gradle:checkCode` lint errors and deprecations.

[sufyanAbbasi]

Seems like there's a growing list of deprecations produced by the gradle:checkCode workflow. We should consider going through them and fixing them all!

• [ ] #2962
• [x] #2960
• [x] #2963
• [x] #2965
• [x] #2967
• [x] #2969
• [x] #2971
• [x] #2973
• [x] #2944
• [x] #2941