WT-12907: give txn read timestamp‘s Abnormal cause

[y123456yz]

Background： in HAVE_DIAGNOSTIC mode, the following code is abnormal, but No root cause was given：
testutil_check(conn->set_timestamp(conn, "oldest_timestamp=10, stable_timestamp=10"));
for (i = 0; i < kv_num; i++) {
error_check(session->begin_transaction(session, NULL));
cursor->set_key(cursor, i); /* Insert a record. */
cursor->set_value(cursor, "value: aaa");
error_check(cursor->insert(cursor));
testutil_check(session->timestamp_transaction(session, "commit_timestamp=20"));
error_check(session->commit_transaction(session, NULL));
}

for (i = 0; i < kv_num; i++) {
    error_check(session->begin_transaction(session, NULL));
    cursor->set_key(cursor, i); /* Insert a record. */
    cursor->set_value(cursor, "value: bbb");
    error_check(cursor->insert(cursor));
    testutil_check(session->timestamp_transaction(session, "commit_timestamp=5"));
    error_check(session->commit_transaction(session, NULL));
}

The log is as follows:
[1714395388:975693][35391:0x7f2b937b8800], WT_SESSION.__session_begin_transaction: [WT_VERB_API][DEBUG_1]: CALL: WT_SESSION:__session_begin_transaction
ex_access: FAILED: access_txn23_test/316: session->begin_transaction(session, "read_timestamp=5"): Invalid argument
ex_access: process aborting
WiredTiger Error: __wt_abort, 28: aborting WiredTiger library
Aborted (core dumped)

after this PR, the log info is:
[1714395512:946863][36783:0x7fa6955e1800], WT_SESSION.__session_begin_transaction: [WT_VERB_API][DEBUG_1]: CALL: WT_SESSION:__session_begin_transaction
[1714395512:946892][36783:0x7fa6955e1800], WT_SESSION.__session_begin_transaction: [WT_VERB_TIMESTAMP][NOTICE]: read timestamp (0, 5) less than the oldest timestamp (0, 16)
ex_access: FAILED: access_txn23_test/316: session->begin_transaction(session, "read_timestamp=5"): Invalid argument
ex_access: process aborting
WiredTiger Error: _wt

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[y123456yz]

WT-12907

[y123456yz]

Since we mask the exception log in the real online production environment, I add a txn_set_read_timestamp_more_than_oldest_timestamp statistic so that we can obtain the exception statistics.
mongo server version 4.2 In a real transaction usage environment, many clusters have this exception logs, If the log is blocked frequently, we cannot get this exception information，It is therefore recommended to add this statistic.