Hide explore results button for no-data users

[daltojohnso]

Fixes #20044

Throwing an additional condition into the hasExploreResultsLink check -- that the question's query is not read-only via:

!question.query().readOnly();

The page blanks out due to a scripting error because there's code in the query builder that assumes there is query metadata--obviously, not the case for a user without permissions. Not doing anything about that since the we shouldn't let users get into this state.

Testing

1. Log into a user without self-serve data permissions
2. Navigate to a saved native question
3. You should not see the "Explore Results" button in the header
4. Log into a user with data permissions
5. Go to the same saved questions
6. You should see the "Explore Results" button in the header

[daltojohnso]

Adding @kulyk to this review directly because you might know a better method to use than question.query().readOnly()

[kulyk]

AFAIK query.readOnly() is the best way out there

[codecov]

Codecov Report

Merging #20065 (1cf0008) into master (385fa88) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #20065   +/-   ##
=======================================
  Coverage   64.79%   64.80%           
=======================================
  Files        2078     2078           
  Lines       73760    73761    +1     
  Branches     8818     8818           
=======================================
+ Hits        47796    47801    +5     
+ Misses      22204    22200    -4     
  Partials     3760     3760           

Flag	Coverage Δ
front-end	44.20% <100.00%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
...abase/query_builder/components/view/ViewHeader.jsx	69.62% <100.00%> (+0.38%)	⬆️
...nd/src/metabase-lib/lib/queries/StructuredQuery.ts	70.78% <0.00%> (+0.22%)	⬆️
...ontend/src/metabase-lib/lib/queries/NativeQuery.ts	75.48% <0.00%> (+1.29%)	⬆️
frontend/src/metabase/lib/greeting.js	76.92% <0.00%> (+7.69%)	⬆️

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