Rollup merge of #141650 - Zalathar:revert-unused-local-file, r=Zalathar

coverage: Revert "unused local file IDs" due to empty function names

The changes to coverage metadata generation in rust-lang/rust#140847 appear to be the most likely cause of the `function name is empty` errors reported in rust-lang/rust#141577.

If that guess is correct, great. If not, no big deal.

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This reverts commit 3b22c21dd8c30f499051fe7a758ca0e5d81eb638, reversing changes made to 5f292eea6d63abbd26f1e6e00a0b8cf21d828d7d.

r? ghost

Author: matthiaskrgr