Improve readability for ingress.yaml under charts/flyte-core/templates/common

[lowc1012]

Tracking issue

Closes #4944

Why are the changes needed?

Because charts/flyte-core/templates/common/ingress.yaml looks messy, it need to be improved for readability

What changes were proposed in this pull request?

1. move grpcRoutes template to _helpers.tpl
2. polish ingress.yaml and separate manifest into ingress.yaml & ingress-separateGrpc.yaml
3. set default .Values.common.ingress.host and ingressClassName as empty string

How was this patch tested?

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

Docs link

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.00%. Comparing base (fd42f65) to head (27da5c2).
Report is 21 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4945   +/-   ##
=======================================
  Coverage   58.99%   59.00%           
=======================================
  Files         645      645           
  Lines       55542    55548    +6     
=======================================
+ Hits        32769    32775    +6     
  Misses      20182    20182           
  Partials     2591     2591           

Flag	Coverage Δ
unittests	59.00% <ø> (+<0.01%)	⬆️

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