Add v2 Proto definitions

[MarlonGamez]

Related: #5368 , #5422, #5423

Description
This PR adds the proto file containing the definitions for message types that will be used as part of the v2 API. Most of this is copy-paste from proto/v1/skaffold.proto. The main changes are to the Event API related messages, as well as the service definition.

Follow-up Work (remove if N/A)

• Add Dockerfile and update scripts to generate proto files
• Metadata proto messages will be updates later based on design from VSC IDE team

[codecov]

Codecov Report

Merging #5415 (4055e0c) into master (2c91d23) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5415      +/-   ##
==========================================
- Coverage   71.39%   71.39%   -0.01%     
==========================================
  Files         399      397       -2     
  Lines       14508    14551      +43     
==========================================
+ Hits        10358    10388      +30     
- Misses       3382     3390       +8     
- Partials      768      773       +5     

Impacted Files	Coverage Δ
pkg/skaffold/test/structure/structure.go	87.50% <0.00%> (-12.50%)	⬇️
pkg/skaffold/util/tar.go	50.66% <0.00%> (-5.34%)	⬇️
pkg/skaffold/runner/new.go	67.58% <0.00%> (-1.70%)	⬇️
pkg/skaffold/docker/image.go	78.13% <0.00%> (-1.40%)	⬇️
pkg/skaffold/test/structure/error.go	100.00% <0.00%> (ø)
pkg/skaffold/instrumentation/types.go	0.00% <0.00%> (ø)
pkg/skaffold/test/error.go
pkg/skaffold/test/test.go
pkg/skaffold/test/structure/types.go
pkg/skaffold/test/test_factory.go	78.94% <0.00%> (ø)
... and 4 more

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[tejal29]

Over all LGTM

1. Remove deprecated fields
2. How can we make enums not version specific.