Do not use Base.get_extension

[tiemvanderdeure]

Drop the use of Base.get_extension in favour of an is_loaded function that is overloaded inside of each extension

Closes #1025

[rafaqz]

Thanks

[asinghvi17]

Why a type and not a singleton?

[rafaqz]

Yeah a singleton is probably marginally better, if you want to change them over @tiemvanderdeure

[asinghvi17]

tiemvanderdeure#4

[codecov]

Codecov Report

❌ Patch coverage is 45.00000% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.69%. Comparing base (f1c4b75) to head (7641dfe).
⚠️ Report is 44 commits behind head on main.

Files with missing lines	Patch %	Lines
src/extensions.jl	80.00%	2 Missing ⚠️
...rmationsExt/RastersCoordinateTransformationsExt.jl	0.00%	1 Missing ⚠️
...t/RastersGRIBDatasetsExt/RastersGRIBDatasetsExt.jl	0.00%	1 Missing ⚠️
ext/RastersMakieExt/RastersMakieExt.jl	0.00%	1 Missing ⚠️
ext/RastersNCDatasetsExt/RastersNCDatasetsExt.jl	0.00%	1 Missing ⚠️
ext/RastersProjExt/RastersProjExt.jl	0.00%	1 Missing ⚠️
...asterDataSourcesExt/RastersRasterDataSourcesExt.jl	0.00%	1 Missing ⚠️
ext/RastersStatsBaseExt/RastersStatsBaseExt.jl	0.00%	1 Missing ⚠️
...t/RastersZarrDatasetsExt/RastersZarrDatasetsExt.jl	0.00%	1 Missing ⚠️
src/methods/reproject.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1027      +/-   ##
==========================================
+ Coverage   82.89%   83.69%   +0.80%     
==========================================
  Files          58       68      +10     
  Lines        5425     5484      +59     
==========================================
+ Hits         4497     4590      +93     
+ Misses        928      894      -34     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[asinghvi17]

Looks good to me! And CI runs