LibraryLoader trait only imports plain source code

[ferranbt]

Before, the LibraryLoader trait was in charge of both loading the source code and generating a Program instance. Now, it only returns the source code.

[codspeed-hq]

Merging this PR will not alter performance

✅ 74 untouched benchmarks

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_{Comparing import-only-source (ab111cc) with main (e9477bc)¹}

Footnotes

1. No successful run was found on main (415e5d1) during the generation of this report, so e9477bc was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩