feat(api/build): add endpoint to get build by id

[ecrupper]

Getting build by ID will be very helpful in a number of ways, but the reason at the top of mind is using this endpoint to retrieve a build that corresponds with a hook on the hooks page in the UI.

One endpoint is for users who have at least read access to the repo in question, and the other is for admins which bypasses that repo check.

Part of the effort for https://github.com/go-vela/community/issues/610 as well.

[codecov[bot]]

Codecov Report

Merging #646 (af2a9d0) into main (09e827e) will decrease coverage by 0.07%. The diff coverage is 41.30%.

@@            Coverage Diff             @@
##             main     #646      +/-   ##
==========================================
- Coverage   54.66%   54.59%   -0.08%     
==========================================
  Files         216      216              
  Lines       16086    16178      +92     
==========================================
+ Hits         8794     8832      +38     
- Misses       6908     6962      +54     
  Partials      384      384              

Impacted Files	Coverage Δ
api/build.go	1.56% <0.00%> (-0.08%)	:arrow_down:
database/postgres/hook.go	92.59% <ø> (ø)
database/sqlite/hook.go	92.59% <ø> (ø)
database/postgres/build.go	95.86% <100.00%> (+0.62%)	:arrow_up:
database/sqlite/build.go	95.86% <100.00%> (+0.62%)	:arrow_up:

[ecrupper]

Yeah, I'm not really sure why I chose write. I think complete parity with the current form of getting a build is the way we want to go. I'll change that now