pkg/cover: refactor extraction of coverage points
pkg/cover: refactor extraction of coverage points

1. Add module.Addr right in objdump, there is not point in the separate loop.
It only adds unnecessary lines of code.

2. Eliminate excessive module.Name == "" checks.
We already check module.Name == "" in makeELF, there is no point
in the separate check in readCoverPoints. It also does 2 completely
different things, it's a bad way to structure code. Split it into
readCoverPoints and readModuleCoverPoints.

3. Refactor readModuleCoverPoints.
It can be much more compact, one reasonably short function.
Also avoid reading ELF symbols for every relocation,
it's completely unnecessary. We already read symbols in readSymbols,
so we don't need to re-read them again at all.

xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller