Compilation message with MPI extension

[ranocha]

I wanted to draft a version with a package extension for MPI so that we can still include the info message

[ Info: You just called `trixi_include`. Julia may now compile the code, please be patient.

However, the first naive approach doesn't work nicely since we're not allowed to overwrite method definitions while precompiling. Thus, I needed to deactivate precompilation for the extension, resulting in the ugly messages

julia> using MPI, TrixiBase
[ Info: Precompiling TrixiBaseMPIExt [722ac391-ce67-58c0-be25-224aa07e4d5d]
[ Info: Skipping precompilation since __precompile__(false). Importing TrixiBaseMPIExt [722ac391-ce67-58c0-be25-224aa07e4d5d].

julia> trixi_include("test/dummy.jl")
[ Info: You just called `trixi_include`. Julia may now compile the code, please be patient.
Hello

We can not use something in __init__ since that will be called before Trixi.jl is initialized - i.e., before MPI is initialized in general.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (1dc5a93) 93.65% compared to head (8bebfd9) 94.36%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5 +/- ## ========================================== + Coverage 93.65% 94.36% +0.71% ========================================== Files 4 4 Lines 63 71 +8 ========================================== + Hits 59 67 +8 Misses 4 4 ```

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[sloede]

@ranocha I think the error message is not yet properly filtered out: https://github.com/trixi-framework/TrixiBase.jl/actions/runs/7711136543/job/21015911732?pr=5#step:7:65

[github-actions[bot]]

Pull Request Test Coverage Report for Build 7726527485

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.7%) to 94.366%

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Totals
Change from base Build 7711120067:	0.7%
Covered Lines:	67
Relevant Lines:	71

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💛 - Coveralls

[ranocha]

@ranocha I think the error message is not yet properly filtered out: https://github.com/trixi-framework/TrixiBase.jl/actions/runs/7711136543/job/21015911732?pr=5#step:7:65

Should be fixed