Make relocation processing consistent across various compilation modes

[dsouzai]

See eclipse-omr/omr#7983 (comment) for context.

At present, external relocation records are generated in a metadata helper method of various instructions. These have been implicitly assumed to only matter for AOT compilations - that is, they may execute in a non-AOT compilation, but the generated relocation records are only processed under an AOT compilation.

However, under JITServer, the relocations are processed regardless of whether the compilation is AOT or not; happens because JITServer needs some subset of the relocation records for non-AOT compilations. However, as the code stands, this is problematic because not all relocation records are valid to process outside of an AOT compilation.

eclipse-omr/omr#7983 fixes one particular issue, but it is not a general solution. A general solution would involve potentially allowing relocation records to get generated during a compile, but only valid ones would be processed. For AOT, all relocations are valid, but for JITServer, only a subset would be valid.

This issue tracks this cleanup work.