Crash in createUserAgentHeader on Android (Port)

Creating a replicator causes the following crash on Android 5 to 8 (~20% of all Android devices):

```

• • • *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
      Build fingerprint: 'Android/sdk_google_phone_x86/generic_x86:5.1.1/LMY48X/6695563:userdebug/test-keys'
      Revision: '0'
      ABI: 'x86'
      pid: 3483, tid: 3502, name: 1.ui >>> com.terwesten.gabriel.cbl_e2e_tests_flutter <<<
      signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
      Abort message: 'stack corruption detected'
      eax 00000000 ebx 00000d9b ecx 00000dae edx 00000006
      esi a209adb8 edi 00000002
      xcs 00000073 xds 0000007b xes 0000007b xfs 00000077 xss 0000007b
      eip b75762e6 ebp 00000dae esp a2099cc0 flags 00200282
      backtrace:
      #00 pc 000742e6 /system/lib/libc.so (tgkill+22)
      #01 pc 0002217b /system/lib/libc.so (pthread_kill+155)
      #02 pc 000239f4 /system/lib/libc.so (raise+36)
      #03 pc 0001bdf4 /system/lib/libc.so (abort+84)
      #04 pc 0001ea60 /system/lib/libc.so (__libc_fatal+32)
      #05 pc 000739fc /system/lib/libc.so (__stack_chk_fail+28)
      #06 pc 000826ce /data/app/com.terwesten.gabriel.cbl_e2e_tests_flutter-1/lib/x86/libcblite.so (createUserAgentHeader()+1486)
      #07 pc 000813d1 /data/app/com.terwesten.gabriel.cbl_e2e_tests_flutter-1/lib/x86/libcblite.so (cbl_internal::ReplicatorConfiguration::ReplicatorConfiguration(CBLReplicatorConfiguration const&)+1489)
      #08 pc 0007d798 /data/app/com.terwesten.gabriel.cbl_e2e_tests_flutter-1/lib/x86/libcblite.so (CBLReplicator::CBLReplicator(CBLReplicatorConfiguration const&)+184)
      #09 pc 0007d60f /data/app/com.terwesten.gabriel.cbl_e2e_tests_flutter-1/lib/x86/libcblite.so (CBLReplicator_Create+95)
      #10 pc 0001a851 /data/app/com.terwesten.gabriel.cbl_e2e_tests_flutter-1/lib/x86/libcblitedart.so (CBLDart_CBLReplicator_Create+513)
      ```

The problem is that `createUserAgentHeader` only allocates 3 bytes for `ro.build.version.release`, which is not enough for some releases, e.g. `5.0.1`.

The docs for [ `__system_property_get`|https://android.googlesource.com/platform/bionic/+/7b95807/libc/include/sys/system_properties.h#47] state that a value can have at most `PROP_VALUE_MAX` bytes.