Make error messages in LaunchPlan.get_or_create actionable

[fg91]

Why are the changes needed?

When registering their applications (tasks, workflows, launchplans), our users are regularly confused by the following exception:

~ pyflyte register ...
  ...
  File ".../wf.py", line 22, in <module>
    lp = LaunchPlan.get_or_create(

  File ".../flytekit/core/launch_plan.py", line 284, in get_or_create
    raise AssertionError("The cached values aren't the same as the current call arguments")

Often, our users think this was related to Flyte's caching mechanism, steering their debugging in the wrong direction.

Actually, the problem occurs when ...

1. ... trying to use the same launch plan name for two different workflows

   @workflow
   def wf():
   
   @workflow
   def wf2():
   
   lp = LaunchPlan.get_or_create(
       wf,
       "my_wf",
   )
   
   lp = LaunchPlan.get_or_create(
       wf2,
       "my_wf",
   )

2. ... or trying to create two launchplans with the same name and for the same workflow but with different arguments:

   lp = LaunchPlan.get_or_create(
       wf,
       "my_wf",
   )
   
   lp = LaunchPlan.get_or_create(
       wf,
       "my_wf",
       schedule=CronSchedule(schedule="0 0 * * *"),
   )

In these condensed examples the error is obvious, in a larger code base with launch plans defined in different modules it often is not.

What changes were proposed in this pull request?

This PR makes makes the error message more actionable. In the two examples above:

Trying to create two launch plans both named 'my_wf' for the workflows 'test.wf.wf2' and 'test.wf.wf' - please ensure unique names.

Trying to create two launch plans for workflow 'test.wf.wf' both named 'my_wf' but with different values for 'schedule' - please use different launch plan names.

How was this patch tested?

Tested using the examples above.

Check all the applicable boxes

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

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 75.92%. Comparing base (1a01368) to head (8fb6d47).
Report is 2 commits behind head on master.

Files	Patch %	Lines
flytekit/core/launch_plan.py	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2451      +/-   ##
==========================================
+ Coverage   72.22%   75.92%   +3.69%     
==========================================
  Files         182      182              
  Lines       18475    18473       -2     
  Branches     3608     3609       +1     
==========================================
+ Hits        13344    14025     +681     
+ Misses       4499     3837     -662     
+ Partials      632      611      -21     

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