tcmalloc: refactor percpu_tcmalloc.h asm chunks

Dedup common rseq asm prologue, tls access operands (currently x86 uses
ifdefs for PIC/PIE) and common input arguments.

In preparation for pulling remaining functions from .S files.

No functional changes intended.

PiperOrigin-RevId: 566481833
Change-Id: I233803bc16375adc3a4394970a43f014b526c6b4