chore: add function to apply template multiple times

[twpayne]

If applied, this commit simplifies the code required to support templated fields in configuration files. This should make it easier to add more templated fields in the future.

As discussed first on Discord.

[codecov]

Codecov Report

Merging #4158 (cbf4d27) into main (5f7be84) will decrease coverage by 0.05%.
The diff coverage is 98.68%.

@@            Coverage Diff             @@
##             main    #4158      +/-   ##
==========================================
- Coverage   84.05%   84.00%   -0.05%     
==========================================
  Files         130      130              
  Lines       12266    12191      -75     
==========================================
- Hits        10310    10241      -69     
+ Misses       1554     1550       -4     
+ Partials      402      400       -2     

Impacted Files	Coverage Δ
internal/pipe/chocolatey/chocolatey.go	76.31% <87.50%> (+2.17%)	⬆️
internal/archivefiles/archivefiles.go	90.19% <100.00%> (-0.46%)	⬇️
internal/pipe/krew/krew.go	79.92% <100.00%> (-0.84%)	⬇️
internal/pipe/nfpm/nfpm.go	92.87% <100.00%> (-0.17%)	⬇️
internal/pipe/nix/nix.go	80.66% <100.00%> (-0.57%)	⬇️
internal/pipe/scoop/scoop.go	75.09% <100.00%> (-1.22%)	⬇️
internal/pipe/snapcraft/snapcraft.go	83.65% <100.00%> (-0.26%)	⬇️
internal/pipe/winget/winget.go	83.33% <100.00%> (-1.36%)	⬇️
internal/tmpl/tmpl.go	98.33% <100.00%> (+0.08%)	⬆️

[caarlos0]

looks great, thanks @twpayne 💜