LoadInternal auto-loads ICU for the named Europe/Brussels zone; when ICU has
no on-disk copy and no network egress (CI test docker, edge/musl, offline) the
auto-load is caught so the extension still loads with the session timezone at
its default. The release/debug/reldebug test targets stage the locally-built
icu.duckdb_extension into the version/platform path DuckDB autoloads from.

DuckDB runs scalar and cast bodies on TaskScheduler worker threads; MEOS keeps
the session timezone, errno, PROJ context and RNGs in thread-local storage and
needs meos_initialize() on each thread before first use. A thread-local guard
in the scalar exec wrapper and a cast trampoline run the per-thread init (and
re-install the error handler) at every entry point, so timestamp formatting on
a worker no longer dereferences a NULL session_timezone.

…pected

The tfloat ln/exp/log10 lifts insert one chord-error turning point on a linear
segment; the MEOS pin computes it in double so the inserted instant is identical
on every platform, and the 026b expected carries the three-instant result.

On macOS LP64 int64 (long) and int64_t (long long) are the same width but
distinct types, so clang rejects bigint_to_set as a Set *(*)(int64_t) non-type
template argument. A forwarder that casts int64_t to int64 fixes the macOS
build; the cast is a no-op on Linux.

Adds the SIZEOF_LONG_LONG emission to the rendered pg_config.h so the
DuckDB-Wasm (wasm32-emscripten / ILP32) build of MEOS no longer fails the
pg_bitutils integer-width check.

The pinned MEOS returns TimeSplit / DatumSplit / IntSplit / FloatSplit /
SpaceSplit / SpaceTimeSplit / MvtGeom structs from the split and
as-mvtgeom functions, and set_vals / set_spans / spanset_spans take an
int* count out-parameter. Adapt the temporal, tgeompoint, set, span and
spanset table/scalar functions to the struct fields and the extra
out-parameter.

Pin MEOS to the canonical ecosystem surface and adapt the binding to it:
treat a shared span boundary as adjacency (the share-a-boundary span
adjacency goldens), and derive the symmetric box/span x temporal
topological predicates (overlaps/same/adjacent) from MEOS's single
canonical argument direction by commutativity, since the reverse-argument
duplicates are deduplicated out of the surface.