fix(native): reduce daemon stack usage

[jpnurmi]

sentry__write_minidump() allocates a ~1.2 MB writer on the stack, including 4,096 memory-map records. Android API 36 e2e tests for #1725 exposed a daemon stack overflow on the crash service's Java worker. Logcat showed SIGSEGV / SEGV_ACCERR before minidump creation.

Heap-allocate minidump_writer_t with SENTRY_MAKE, preserving zero initialization and freeing it on every exit.

[codecov]

Codecov Report

❌ Patch coverage is 23.52941% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.38%. Comparing base (4ce28e7) to head (7fbd5fa).

Additional details and impacted files

@@            Coverage Diff             @@
##               v1    #2211      +/-   ##
==========================================
+ Coverage   75.13%   75.38%   +0.25%     
==========================================
  Files         104      104              
  Lines       29630    29642      +12     
  Branches     5479     5480       +1     
==========================================
+ Hits        22263    22347      +84     
+ Misses       5960     5874      -86     
- Partials     1407     1421      +14     

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