feature(events): new event for catching oversized allocation

[fruch]

new everytime we'll have those we'll have an error event for it

2025-03-24T12:58:48.953+00:00 rolling-upgrade--ubuntu-focal-db-node-1b73896e-eastus-4  !WARNING |
scylla[13320]:  [shard 0:strm] seastar_memory - oversized allocation: 1409024 bytes.
This is non-fatal, but could lead to latency and/or fragmentation issues.
Please report: at 0x26f152e 0x26f0fc0 0x26f0f98 0x518d2fc 0x176c134 0x15c0a44 0x271fe5c
0x2fb90dd 0x1d3c4c6 0x30d3df7 0x30d2b0c 0x2cb3099 0x2cb2a72 0x29526de
0x295a78d /opt/scylladb/libreloc/libc.so.6+0x2a087 /opt/scylladb/libreloc/libc.so.6+0x2a14a
0x319a844

Ref: scylladb/scylladb#23446 (comment)

Testing

• [ ]

PR pre-checks (self review)

• I added the relevant backport labels
• I didn't leave commented-out/debugging code

Reminders

• Add New configuration option and document them (in sdcm/sct_config.py)
• Add unit tests to cover my changes (under unit-test/ folder)
• Update the Readme/doc folder relevant to this change (if needed)