libarchive: import changes from upstream

Libarchive 3.6.0

New features:
PR #1614: tar: new option "--no-read-sparse"
PR #1503: RAR reader: filter support
PR #1585: RAR5 reader: self-extracting archive support

New features (not used in FreeBSD base):
PR #1567: tar: threads support for zstd (#1567)
PR #1518: ZIP reader: zstd decompression support

Security Fixes:
PR #1491, #1492, #1493, CVE-2021-36976:

fix invalid memory access and out of bounds read in RAR5 reader

PR #1566, #1618, CVE-2021-31566:

extended fix for following symlinks when processing the fixup list

Other notable bugfixes and improvements:
PR #1620: tar: respect "--ignore-zeros" in c, r and u modes
PR #1625: reduced size of application binaries

MFC after: 2 weeks
Relnotes: yes