This should be able to unblock using grpc on vision os, will add tests later
Closes#36476
COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36476 from HannahShiSFB:support-visionos edbde32d23
PiperOrigin-RevId: 630173448
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Follow-up to add privacy manifests to #35042
- [x] Update podspec template files
- [x] Align on manifest update:
```
git grep mach_absolute_time
src/core/lib/gpr/posix/time.cc:static uint64_t g_time_start = mach_absolute_time();
src/core/lib/gpr/posix/time.cc: ((double)(mach_absolute_time() - g_time_start)) * g_time_scale;
```
cc: @paulb777Closes#35542
COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35542 from ncooke3:nc/privacy-manifests b0e0e57d2e
PiperOrigin-RevId: 600595032
Not sure if we need to do the same for all the podspec files.
Will create a separate PR for swift package.
Closes#35042
COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35042 from HannahShiSFB:privacy-manifests c9b19d3c20
PiperOrigin-RevId: 588937122
Upgrade apple platform deployment_target versions to fix the cocoapods
push of BoringSSL-GRPC about the following error:
```
ld: file not found: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/arc/libarclite_macosx.a
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
ref: https://developer.apple.com/forums/thread/725300
This also aligns with the versions required by
[protobuf](https://github.com/protocolbuffers/protobuf/pull/10652)
```
ios.deployment_target = '10.0'
osx.deployment_target = '10.12'
tvos.deployment_target = '12.0'
watchos.deployment_target = '6.0'
```