Feat: Support per-launch plan notification template

[peterxcli]

Tracking issue

Why are the changes needed?

What changes were proposed in this pull request?

Currently we can only define one mail template in config, when some specific workflow state defined in launch plan is reached, then some mails with the mail template in config would sent to recipients.

This PR aims to allow user to define customize notification template for each launch plan.
Demo:

my_notifying_lp = LaunchPlan.create(
    "my_notifying_lp",
    my_workflow_definition,
    default_inputs={"a": 4},
    notifications=[
        Email(
            phases=[WorkflowExecutionPhase.SUCCEEDED],
            recipients_email=["admin@example.com"],
            template="{{ workflow.id }} is ..."
        )
    ],
)

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

Attention: Patch coverage is 31.81818% with 15 lines in your changes missing coverage. Please review.

Project coverage is 37.09%. Comparing base (ab04192) to head (fde5626).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
flyteidl/gen/pb-go/flyteidl/admin/common.pb.go	0.00%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6064      +/-   ##
==========================================
+ Coverage   37.08%   37.09%   +0.01%     
==========================================
  Files        1318     1318              
  Lines      132284   132347      +63     
==========================================
+ Hits        49062    49100      +38     
- Misses      78950    78975      +25     
  Partials     4272     4272              

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (ø)
unittests-flyteadmin	54.08% <100.00%> (-0.02%)	⬇️
unittests-flytecopilot	30.99% <ø> (ø)
unittests-flytectl	62.29% <ø> (-0.05%)	⬇️
unittests-flyteidl	7.23% <0.00%> (-0.01%)	⬇️
unittests-flyteplugins	53.82% <ø> (+0.09%)	⬆️
unittests-flytepropeller	42.63% <ø> (ø)
unittests-flytestdlib	57.59% <ø> (+0.05%)	⬆️

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