Update text formatting for trap OIDs

[WinstonLobo]

ec: split SNMP trap varbinds across visual lines in event message

Trap events created from incoming SNMP traps concatenate all OID/value pairs into a single long line, which makes the Event Console message column hard to read when a trap carries many varbinds (typical for hardware traps from Dell iDRAC, HP iLO, Microsoft, VMware, etc.).

Use the existing "\x01" line-break marker convention instead of ", " as the separator between varbinds. The GUI painter for the event_text column already converts "\x01" into "
" at render time (see cmk/gui/mkeventd/views.py), so this produces a visual line break per varbind in the Event Console without changing the on-disk format in any incompatible way.

scrub_string() is applied per varbind rather than to the joined string, because it strips "\x01" (along with other control characters) to keep the line-oriented history files safe. Applying it before the join preserves the separator while still sanitising each individual OID/value pair.

Note for rule authors: rules matching the previous ", " separator in trap message text need to be updated, as varbinds are now separated by "\x01" internally.

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