sbpf: undo rodata footprint optimization

[ripatel-fd]

This commit increases the ELF loader's rodata_footprint to be equal
to the ELF file size. This increases memory usage by 5-10% for most
contracts.

The ELF loader made an incorrect assumption that relocations outside
of the rodata segment are invisible to the virtual machine. The
loader therefore reduced the rodata segment size and skipped those
relocations.

This is problematic for two reasons:

1. R_BPF_64_32 can read ~15 bytes past the end of the rodata region
   and conditionally fails loading depending on the content that was
   read.
2. Some relocations move information from high bits to low bits
   within a 64-bit value. Chaining those relocations thus allows
   moving information from outside the rodata segment into the
   rodata segment.

fd_sbpf_loader would have the wrong execution result in both cases.