Fix types in trace

[Foxpunk]

Problem

• A loop variable used MetaId (USHORT), a type not intended for
  holding counts, to iterate up to m_info.pin_count (type size_t),
  risking narrowing and a potential infinite loop.
• MessageSet used int for message codes that are always within a
  small fixed range, wider than necessary.

Fix

• Changed the loop variable type to FB_SIZE_T to match the type of
  m_info.pin_count it's compared against, avoiding narrowing.
• Changed MessageSet fields to USHORT.

Notes

• Changing pin_count's type isn't an option since PerformanceInfo is
  a public struct used outside this file — that would be an API change.
  Casting pin_count at the comparison would just hide the mismatch
  rather than fix it: i is used as an array index into
  m_tableCounters, not as a MetaId, so MetaId was the wrong type
  here regardless of pin_count's type. Widening the loop variable to
  FB_SIZE_T fixes the actual type mismatch and removes the risk of
  overflow/infinite loop if pin_count ever grows beyond USHORT range.
• MessageSet fields were changed to USHORT. All current usages
  (MAIN_USAGE, EXAMPLES) are initialized with message codes in range
  3..42, e.g. MAIN_USAGE{{3, 21}, {41}}, EXAMPLES{{22, 27}, {42}} —
  well within USHORT (0..65535). If new codes are added in the future,
  make sure they still fit into USHORT.

[hvlad]

I have no idea why MetaId appeared here