LU-10499 pcc: test interoperability with PCC-RO

LU-10499 pcc: test interoperability with PCC-RO

For Lustre 2.15.0 servers, it fails many of subtests that are
PCC-RO specific.
In this patch, each subtest related to PCC-RO adds an connect
flag check and skip it when run against old servers without
PCC-RO support.

EX-4006 pcc: make "pccro=1" default

To avoid a risk that users will accidentally configure PCC-RW and
potentially lose data if those client nodes go offline, this patch
makes "pccro=1" default for PCC backends.

This patch adds a new option "--w|--write" for PCC-RW cache
mode when attach a file.
Also It makes "--r|--readonly" as a default option for PCC attach
command.
Was-Change-Id: I56735b0ebe8f0d9ef22b3f7e39e8cccfa3aad443

EX-8739 tests: skip sanity-pcc tests on el9.3

Skip sanity-pcc test_6, test_7a/7b, test_23, test_35 on RHEL9.3
clients due to continuous failures with PCC-RW, which is unused.

Skip sanity-pcc test_102 due to el9.3 fio io_uring bug.
Was-Change-Id: I76cbd0342788fff8b0167c0656e941f96d73fc48

EX-bug-id: EX-2860 EX-4006 EX-8739
Test-Parameters: clientdistro=el9.3 serverversion=EXA6 serverdistro=el8.8 testlist=sanity-pcc
Test-Parameters: clientdistro=el8.9 serverversion=EXA6 serverdistro=el8.8 testlist=sanity-pcc
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: Ie4fc41b2dc51a038027009fbcc6e86f9d61cd54f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54386
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>