There are several prominent keepers like Gilchrist, Dhoni and Knott who played all their Tests as keepers. Others took on keeping duties for one or more Tests when the regular keeper was unavailable. And some took over the keeping duties in the middle of a Test and took catches as well as stumped batsmen.
Statsguru does list “catches as keeper” and “catches as fielder” in separate columns, so we can identify catches taken by short-term keepers. There are even a few cases of substitute fielders going on the field to keep wickets and accounting for catches and stumpings. These were in the earlier days.
Here we look at the cases of those who took at least 10 catches as a keeper and 10 as non-keeper.

There are numerous “multitaskers” from recent years, such as Watling (239 dismissals as keeper and 10 as a fielder). Others are ABD (106 and 121), Bairstow (186 and 11), Buttler (86 and 23) and Chandimal (72 and 15). We can see that ABD is the only one whose dismissals in both categories are roughly the same.
Now we look at those who played at least 5 Tests as keepers and 5 Tests as non-keepers:

From recent years there are Watling, de Villiers, Bairstow, Mushfiqur, Buttler, Chandimal, Wade, KD Karthik, Liton and Kusal Perera.
Karthik is the only Indian player here. Oddly enough, the only players from before 2000 are CL Walcott and WB Philips.