Ensure target-multiversioning emits deferred declarations

As reported in PR50025, sometimes we would end up not emitting functions
needed by inline multiversioned variants. This is because we typically
use the 'deferred decl' mechanism to emit these.  However, the variants
are emitted after that typically happens.  This fixes that by ensuring
we re-run deferred decls after this happens. Also, the multiversion
emission is done recursively to ensure that MV functions that require
other MV functions to be emitted get emitted.