all: go test skip on missing tools

Created by: keegancsmith

A good property we used to have (and should keep) is that go test -short ./... just works, and go test ./... works if you have our important services running (redis/postgres). This PR fixes up some cases where this could fail.

In particular if you don't have comby on your path the test skips (we use the same pattern for other tool dependencies). We also use a custom build of universal-ctags for symbols, so if you have the normal version on your path we don't fail tests due to it failing to start.

In both cases we do fail if we are on CI, to ensure we don't regress.

Test plan:

Created by: codecov[bot]

Codecov Report

Merging #5164 into master will decrease coverage by <.01%. The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #5164      +/-   ##
==========================================
- Coverage   46.21%   46.21%   -0.01%     
==========================================
  Files         735      735              
  Lines       45074    45077       +3     
  Branches     2604     2604              
==========================================
  Hits        20831    20831              
- Misses      22230    22233       +3     
  Partials     2013     2013

Impacted Files	Coverage Δ
cmd/symbols/internal/pkg/ctags/parser.go	0% <0%> (ø)