Simplify --timestamps output

[MarlonGamez]

Fixes #6148

Description
This PR changes the way we setup timestamp output when specifying with --timestamps=true. Previous implementation caused unnecessarily verbose output including irrelevant level field, due to setting up through logrus. New setup also allows us to retain color output while using timestamps.

Before:

time="2021-07-04T19:35:19-07:00" level=info msg="Listing files to watch..."
time="2021-07-04T19:35:19-07:00" level=info msg=" - leeroy-web"
time="2021-07-04T19:35:19-07:00" level=info msg=" - leeroy-app"
time="2021-07-04T19:35:19-07:00" level=info msg="Generating tags..."
time="2021-07-04T19:35:19-07:00" level=info msg=" - leeroy-web -> gcr.io/marlongamez-main/leeroy-web:7c50bd1"
time="2021-07-04T19:35:19-07:00" level=info msg=" - leeroy-app -> gcr.io/marlongamez-main/leeroy-app:7c50bd1"
time="2021-07-04T19:35:19-07:00" level=info msg="Checking cache..."
time="2021-07-04T19:35:21-07:00" level=info msg=" - leeroy-web: Found Remotely"
time="2021-07-04T19:35:21-07:00" level=info msg=" - leeroy-app: Found Remotely"

After:

2021-07-04 19:35:57 Listing files to watch...
2021-07-04 19:35:57  - leeroy-web
2021-07-04 19:35:57  - leeroy-app
2021-07-04 19:35:57 Generating tags...
2021-07-04 19:35:57  - leeroy-web -> 2021-07-04 19:35:57 gcr.io/marlongamez-main/leeroy-web:7c50bd1
2021-07-04 19:35:57  - leeroy-app -> 2021-07-04 19:35:57 gcr.io/marlongamez-main/leeroy-app:7c50bd1
2021-07-04 19:35:57 Checking cache...
2021-07-04 19:35:59  - leeroy-web: 2021-07-04 19:35:59 Found Remotely
2021-07-04 19:35:59  - leeroy-app: 2021-07-04 19:35:59 Found Remotely

[codecov]

Codecov Report

Merging #6146 (410f906) into master (2d766a1) will increase coverage by 0.05%.
The diff coverage is 71.42%.

@@            Coverage Diff             @@
##           master    #6146      +/-   ##
==========================================
+ Coverage   69.93%   69.98%   +0.05%     
==========================================
  Files         481      481              
  Lines       18337    18339       +2     
==========================================
+ Hits        12824    12835      +11     
+ Misses       4561     4553       -8     
+ Partials      952      951       -1     

Impacted Files	Coverage Δ
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
pkg/skaffold/build/result.go	83.33% <0.00%> (ø)
pkg/skaffold/output/output.go	80.00% <81.81%> (-0.65%)	⬇️
cmd/skaffold/app/cmd/cmd.go	71.59% <100.00%> (+2.84%)	⬆️
pkg/skaffold/docker/parse.go	86.19% <0.00%> (-0.96%)	⬇️
pkg/skaffold/output/color.go	95.74% <0.00%> (+4.25%)	⬆️
pkg/skaffold/util/tar.go	56.00% <0.00%> (+5.33%)	⬆️

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