SUBMARINE-1350. Optimize helm template

[cdmikechen]

What is this PR for?

Additional configuration of some helm templates to allow users to better follow the subamrine

What type of PR is it?

Improvement

Todos

• [x] - Add imagePullSecrets
• [x] - Add description and seldon-core istio gateway config
• [x] - Add README
• [x] - Fix quickstart description

What is the Jira issue?

https://issues.apache.org/jira/browse/SUBMARINE-1350

How should this be tested?

NA

Screenshots (if appropriate)

NA

Questions:

• Do the license files need updating? No
• Are there breaking changes for older versions? No
• Does this need new documentation? Yes

[codecov[bot]]

Codecov Report

Merging #1021 (e11f62f) into master (f492e42) will increase coverage by 50.35%. The diff coverage is n/a.

@@              Coverage Diff              @@
##             master    #1021       +/-   ##
=============================================
+ Coverage     25.48%   75.83%   +50.35%     
=============================================
  Files           358      112      -246     
  Lines         29089     4945    -24144     
  Branches       3479        0     -3479     
=============================================
- Hits           7412     3750     -3662     
+ Misses        21461     1195    -20266     
+ Partials        216        0      -216     

Flag	Coverage Δ
python-integration	59.59% <ø> (ø)
python-unit	52.19% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ver/database/workbench/service/SysUserService.java
...mitter/k8s/model/common/PersistentVolumeClaim.java
...g/apache/submarine/server/api/spec/KernelSpec.java
...rg/apache/submarine/server/rest/RestConstants.java
.../submarine/server/utils/response/JsonResponse.java
...rine/server/submitter/k8s/util/MLJobConverter.java
...experiment/codelocalizer/HTTPGitCodeLocalizer.java
.../apache/submarine/server/api/workbench/Action.java
...s/experiment/codelocalizer/DummyCodeLocalizer.java
...ubmarine/server/api/common/CustomResourceType.java
... and 236 more

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