Add deployment trace model encode/decode logic for MySQL datastore

[khanhtc1202]

What this PR does:

as title

Why we need it:

Without this, in case of using MySQL as the datastore of PipeCD control plane, the datastore backend doesn't understand how to encode model object to store to MySQL table 😓

We will get the below error

caller: "mysql/mysql.go:159"
error: "*model.DeploymentTrace is not supported"
kind: "DeploymentTrace"
logger: "pipecd.server"
message: "failed to create entity: failed to encode json data"

Which issue(s) this PR fixes:

Follow PR #5622

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[ffjlabo]

👍

[Warashi]

LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 25.56%. Comparing base (16089a9) to head (5011b59).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/datastore/mysql/model_wrapper.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5651      +/-   ##
==========================================
- Coverage   25.56%   25.56%   -0.01%     
==========================================
  Files         477      477              
  Lines       51080    51088       +8     
==========================================
  Hits        13060    13060              
- Misses      37015    37023       +8     
  Partials     1005     1005              

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