[vm/aot] Delay relocated address calculation for static symbols.

Since we no longer add the symbol for a given code object to the Elf
object when writing the contents of the text segment, we don't need to
calculate the relocated address that early. Instead, just store which
text segment the instructions payload belongs to as well as its offset
into the segment contents and let Elf::Finalize() calculate the
relocated address when creating the symbol.

This removes one need for knowing the segment base address when writing
the segment contents. The remaining needs are related to BSS usage:

* Calculating the BSS offset from the text segment for the Image header.
* Fixing up BSS relocations in instructions payloads.

Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-release-simarm_x64-try
Change-Id: I8be860a7a7111721e6f546154a0814f4d16ac634
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150929
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Clement Skau <cskau@google.com>