[SDK] Fix overflow in timeout logic

[punya]

Also use steady clock consistently.

Prior to this change, the test would fail under ASAN:

$ bazel test --config=asan --test_output=errors //sdk/test/metrics:meter_provider_sdk_test
INFO: Analyzed target //sdk/test/metrics:meter_provider_sdk_test (0 packages loaded, 0 targets configured).
FAIL: //sdk/test/metrics:meter_provider_sdk_test (see /private/var/tmp/_bazel_punya/e3bd968ba61238cdeb1a5537fc3dbf7d/execroot/_main/bazel-out/darwin_arm64-fastbuild-asan/testlogs/sdk/test/metrics/meter_provider_sdk_test/test.log)
INFO: From Testing //sdk/test/metrics:meter_provider_sdk_test:
==================== Test output for //sdk/test/metrics:meter_provider_sdk_test:
Running main() from gmock_main.cc
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from MeterProvider
[ RUN      ] MeterProvider.GetMeter
[Warning] File: sdk/src/metrics/meter_provider.cc:65 [MeterProvider::GetMeter] Library name is empty.
[Warning] File: sdk/src/metrics/meter_provider.cc:65 [MeterProvider::GetMeter] Library name is empty.
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/__chrono/duration.h:102:59: runtime error: signed integer overflow: 9221646818050376183 * 1000 cannot be represented in type '_Ct' (aka 'long long')
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/__chrono/duration.h:102:59 in 
================================================================================
INFO: Found 1 test target...
Target //sdk/test/metrics:meter_provider_sdk_test up-to-date:
  bazel-bin/sdk/test/metrics/meter_provider_sdk_test
INFO: Elapsed time: 2.251s, Critical Path: 2.13s
INFO: 5 processes: 5 darwin-sandbox.
INFO: Build completed, 1 test FAILED, 5 total actions
//sdk/test/metrics:meter_provider_sdk_test                               FAILED in 0.6s
  /private/var/tmp/_bazel_punya/e3bd968ba61238cdeb1a5537fc3dbf7d/execroot/_main/bazel-out/darwin_arm64-fastbuild-asan/testlogs/sdk/test/metrics/meter_provider_sdk_test/test.log

Executed 1 out of 1 test: 1 fails locally.

[lalitb]

LGTM. thanks for the fix.

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.66%. Comparing base (497eaf4) to head (200f6ab).
Report is 122 commits behind head on main.

Files with missing lines	Patch %	Lines
sdk/src/metrics/meter_context.cc	70.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3046      +/-   ##
==========================================
+ Coverage   87.12%   87.66%   +0.55%     
==========================================
  Files         200      190      -10     
  Lines        6109     5866     -243     
==========================================
- Hits         5322     5142     -180     
+ Misses        787      724      -63     

Files with missing lines	Coverage Δ
...metrics/export/periodic_exporting_metric_reader.cc	81.74% <100.00%> (+2.39%)	⬆️
sdk/src/metrics/meter_context.cc	76.06% <70.00%> (-0.65%)	⬇️

... and 122 files with indirect coverage changes