Merge branch 'selftests/bpf: Optimize kallsyms cache'

Rong Tao says:

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We need to optimize the kallsyms cache, including optimizations for the
number of symbols limit, and, some test cases add new kernel symbols
(such as testmods) and we need to refresh kallsyms (reload or refresh).
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>