[ELF] --icf: don't fold text sections with LSDA

[ELF] --icf: don't fold text sections with LSDA

Fix PR36272 and PR46835

A .eh_frame FDE references a text section and (optionally) a LSDA (in
.gcc_except_table).  Even if two text sections have identical content and
relocations (e.g. a() and b()), we cannot fold them if their LSDA are different.

```
void foo();
void a() {
  try { foo(); } catch (int) { }
}
void b() {
  try { foo(); } catch (float) { }
}
```

Scan .eh_frame pieces with LSDA and disallow referenced text sections to be
folded. If two .gcc_except_table have identical semantics (usually identical
content with PC-relative encoding), we will lose folding opportunity.
For ClickHouse (an exception-heavy application), this can reduce --icf=all efficiency
from 9% to 5%. There may be some percentage we can reclaim without affecting
correctness, if we analyze .eh_frame and .gcc_except_table sections.

gold 2.24 implemented a more complex fix (resolution to
https://sourceware.org/bugzilla/show_bug.cgi?id=21066) which combines the
checksum of .eh_frame CIE/FDE pieces.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D84610