[common] Compare maps of different representations without throwing

[PDGGK]

Purpose

Closes #9210.

InternalRowUtils.equals picked the GenericMap fast path by testing data1, then cast data2 with no test of its own:

if (data1 instanceof GenericMap) {
    map1 = (GenericMap) data1;
    map2 = (GenericMap) data2;      // BinaryMap -> ClassCastException

so equals(generic, binary, mapType) throws while equals(binary, generic, mapType) returns true.

Two things say this is unintended rather than a restriction:

• The else branch exists because the representation varies. One MapType is carried by GenericMap, BinaryMap or ColumnarMap interchangeably; the conversion is there to normalise exactly that. Gating it on data1's concrete class contradicts the branch it guards.
• InternalRowUtils.hash already treats them as interchangeable, returning the same value for both. The class says "equal" by hash and throws when asked directly.

Each operand is now converted on its own, keeping the fast path when both are already GenericMap.

Scope, deliberately narrow. The other casts in this method — (InternalRow) data2, (InternalArray) data2 — look like the same shape but are interface casts, and every representation implements those interfaces, so they cannot fail this way. Only the map branch casts to a concrete class. I have left them alone.

Tests

One case in InternalRowUtilsTest asserting three things:

assertion	before
hash(generic) == hash(binary)	green — this is what pins the intent
equals(binary, generic)	green
equals(generic, binary)	ClassCastException

Only the third changes. The other two being green both before and after is the point: they establish that the two representations were already meant to be equivalent, so the third is a defect rather than a new feature.

InternalRowUtilsTest ... ClassCastException: class BinaryMap cannot be cast to class GenericMap
Tests run: 7, Failures: 0, Errors: 1      <- master

Tests run: 7, Failures: 0, Errors: 0      <- with the fix

Related suites pass (InternalRowSerializerTest, RowCompactedSerializerTest). spotless:check and checkstyle:check exit 0.