linker: Add indirect relocations

[benjaminkasper99]

Add the capability to generate indirect relocations to the OpenVADL linker.

An example of such a relocation is pcrel_lo of RISCV, where the relocation's type depends on the type of its paired relocation.

.Lpcrel_hi0:
   auipc   a0, %got_pcrel_hi(Coeff)
   ld      a0, %pcrel_lo(.Lpcrel_hi0)(a0)}

Here the %pcrel_lo relocation is paired with a global offset table (GOT) relocation, therefore %pcrel_lo is also GOT relative.

.Lpcrel_hi0:
   auipc   a0, %pcrel_hi(Coeff)
   ld      a0, %pcrel_lo(.Lpcrel_hi0)(a0)}

In this case %pcrel_lo is paired with a PC relative relocation, therefore %pcrel_lo also is just PC relative.

Notable changes in this PR:

• Added the paired annotation to relocation definitions, to declare which relocations should behave as described above
• Added two LLD templates, in which the relocation indirection is implemented
• Moved pseudo expansion within the assembler from code emitter to parser, since access to a streamer is needed to emit labels. This also required to adjust the asm parser filecheck tests to check the expanded state of instructions.
• Added a Riscv64 LCB integration test (LcbRiscv64SimulationTest)
• Re-enabled two code emitter tests (disabled in frontend: Add NewLabelStatement and LabelType #1064)
• Adjusted label names in LLVM IR filecheck tests

[Jozott00]

LGTM, although i just did a structural check rather than a semantic one