feat(go): support case-insensitive column names on reads

[jackylee-ch]

Purpose

Follow-up to #496, which added this read-time switch to the core, the C ABI and
Python and left "Go's own opt-in case-insensitive API" to a follow-up. Measured
from Go, fixture columns lowercase:

NewRead() after WithProjection([ID NAME]) -> Column ID does not exist in table ...
pb.Eq("ID", 1)                            -> Column 'ID' not found in schema fields ["id", "name"]

Neither half is reachable from Go, and the first message names the column absent
when only its case differs.

Brief change log

One switch name, WithCaseSensitive, on each object that owns a name resolution:
ReadBuilder for projection, PredicateBuilder for predicates. The split is
core's and the C ABI's, not Go's: the core resolves a column when the predicate is
built, so a read-builder flag cannot reach an already-built one. Python needs a
single switch only because its filter is a dict converted at with_filter time,
while Go's WithFilter takes a resolved handle.

Table gains no method; PredicateBuilder.WithCaseSensitive returns a copy. The
ten predicates Go exposes now call the additive
paimon_predicate_*_with_case_sensitive entry points, the default passing true.
The six operators C gained in #523 but Go never bound stay out of scope.

Tests

Asserted in both directions: unset and true still reject uppercase names,
false resolves them, records come back with the schema's own spelling, and both
call orders agree. Each of the three predicate argument shapes has a case, and one
test pins that neither switch reaches the other.

API and Format

Two new Go methods, one name. No ABI, wire or storage change; the C symbols
already exist.

Documentation

One go-binding.md section per half.

[JingsongLi]

Why we need to add this API? Only for GO?

[jackylee-ch]

Not Go-only: the split is core's and the C ABI's, both merged in #496, whose description left Go's half to a follow-up. Python needs a single switch only because its filter is a dict converted at with_filter time; Go's WithFilter takes an already-resolved handle, so the flag has to sit on the builder that produces the predicate.

Collapsed it into PredicateBuilder.WithCaseSensitive in 23e53fa so both halves share one switch name and Table gains no method. go test ./... in bindings/go green, including a new test pinning that neither switch reaches the other.