Add heap alignment workaround for ESP32-S3 operator new

[ltowarek]

Summary

• Adds src/esp_heap_align.cpp — replaces the six standard replaceable allocation operators (operator new, operator new[], and their delete counterparts) with versions backed by heap_caps_aligned_alloc(alignof(max_align_t), ...), making operator new conforming on ESP32-S3
• Adds Kconfig with a new ESP_OPENTELEMETRY_HEAP_ALIGN_WORKAROUND bool option (default y)
• Updates CMakeLists.txt to conditionally compile esp_heap_align.cpp and pull it onto the link line via -Wl,--undefined=_Znwj
• Adds two standalone test applications under test/:
  • heap_align_idf — pure ESP-IDF alignment survey (no external libs); shows which allocations violate the C/C++ standard
  • heap_align_protobuf — uses protobuf's Arena with the exact ArenaOptions from OtlpHttpExporter; reproduces the InstrFetchProhibited crash at PC=0x00010000 without the workaround

Background

ESP-IDF's multi_heap.c uses sizeof(void*)=4 as its alignment granularity. The ESP32-S3 toolchain reports alignof(std::max_align_t)==8. Protobuf's TaggedAllocationPolicyPtr stores control flags in the low 3 bits of a pointer (kPtrMask = ~7), requiring 8-byte alignment. When operator new returns a 4-byte-aligned block, get() computes ptr & ~7 = ptr - 4, reading max_block_size (0x00010000) as the block_alloc function pointer — crashing with InstrFetchProhibited at PC=0x00010000. Tracked in issue #32.

Test plan

• Build test/heap_align_protobuf with CONFIG_ESP_OPENTELEMETRY_HEAP_ALIGN_WORKAROUND=y (default) — confirm it prints PASS: Arena survived second-block allocation
• Build with CONFIG_ESP_OPENTELEMETRY_HEAP_ALIGN_WORKAROUND=n — confirm it crashes with InstrFetchProhibited at PC=0x00010000
• Build test/heap_align_idf — confirm Non-conforming: 0 / 16 with workaround enabled