[sanitizer] Simplify GetTls with dl_iterate_phdr on Linux

This was reverted by f176803e due to
Ubuntu 16.04 x86-64 glibc 2.23 problems.
This commit additionally calls `__tls_get_addr({modid,0})` to work around the
dlpi_tls_data==NULL issues for glibc<2.25
(https://sourceware.org/bugzilla/show_bug.cgi?id=19826)

GetTls is the range of

* thread control block and optional TLS_PRE_TCB_SIZE
* static TLS blocks plus static TLS surplus

On glibc, lsan requires the range to include
`pthread::{specific_1stblock,specific}` so that allocations only referenced by
`pthread_setspecific` can be scanned.

This patch uses `dl_iterate_phdr` to collect TLS blocks. Find the one
with `dlpi_tls_modid==1` as one of the initially loaded module, then find
consecutive ranges. The boundaries give us addr and size.

This allows us to drop the glibc internal `_dl_get_tls_static_info` and
`InitTlsSize` entirely. Use the simplified method with non-Android Linux for
now, but in theory this can be used with *BSD and potentially other ELF OSes.

This simplification enables D99566 for TLS Variant I architectures.

See https://reviews.llvm.org/D93972#2480556 for analysis on GetTls usage
across various sanitizers.

Differential Revision: https://reviews.llvm.org/D98926