Strip away debug info not needed by BPF programs (and subprograms used by them)

[vadorovsky]

Currently, when we link bitcodes with debug info, even though we fix up it, we don't strip it. That produces a lot of unnecessary DI.

For example, if lto is not used, the debug info of core crate and other dependencies will end up in the BTF too. That makes the BTF relocations and program verification slower. It's also not correct by principle.

Context: https://discord.com/channels/855676609003651072/1026937450624450652/1133054554666180678