ORC-2027: [C++] Fix undefined behavior in DoubleColumnReader::readFloat()

### What changes were proposed in this pull request?

Unaligned reads are UB in C++. We can not guarantee that the `bufferPointer_` pointer is aligned by `alignof(int32_t)`.

### How was this patch tested?
Use UBsan to test in private repo.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes #2444 from HuaHuaY/fix_issue_2027.

Lead-authored-by: Zehua Zou <zehuazou2000@gmail.com>
Co-authored-by: Zehua Zou <41586196+HuaHuaY@users.noreply.github.com>
Signed-off-by: Gang Wu <ustcwg@gmail.com>
(cherry picked from commit c4fa9fa)
Signed-off-by: Gang Wu <ustcwg@gmail.com>

Author: HuaHuaY

c++/src/ColumnReader.cc

@@ -421,7 +421,7 @@ namespace orc {
       int32_t bits = 0;
       if (bufferEnd_ - bufferPointer_ >= 4) {
         if (isLittleEndian) {
-          bits = *(reinterpret_cast<const int32_t*>(bufferPointer_));
+          memcpy(&bits, bufferPointer_, sizeof(bits));
         } else {
           bits = static_cast<unsigned char>(bufferPointer_[0]);
           bits |= static_cast<unsigned char>(bufferPointer_[1]) << 8;