fix: interaction of extern annotations and calls to functions with borrowed parameters

[hargoniX]

This PR fixes a bug in the borrow inference in connection with export annotations.

Previously parameters of export functions were presumed as owned from the beginning of the
analysis. However, they were not added into the set of owned parameters and thus sometimes failed to
force necessary changes to borrowedness of other values that the parameters flowed into.

[hargoniX]

!bench

[leanprover-radar]

Benchmark results for b3e83d2 against 189cea9 are in. There are no significant changes. @hargoniX

• 🟥 build//instructions: +1.0G (+0.01%)

Medium changes (1✅)

• ✅ interpreted/identifier_completion//instructions: -1.1G (-1.42%)

Small changes (1✅, 2🟥)

• 🟥 build/module/Lean.Compiler.LCNF.InferBorrow//instructions: +270.1M (+4.14%) (reduced significance based on *//lines)
• 🟥 compiled/rbmap_checkpoint//instructions: +3.0M (+0.02%)
• ✅ interpreted/identifier_completion//wall-clock: -105ms (-2.49%)