feat(metrics): Add implementation for metrics envelope item

[philprime]

:scroll: Description

This PR must be merged after #6956 and #6957

:bulb: Motivation and Context

Closes #6951

:green_heart: How did you test it?

:pencil: Checklist

You have to check all boxes before merging:

• [ ] I added tests to verify the changes.
• [ ] No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• [ ] I updated the docs if needed.
• [ ] I updated the wizard if needed.
• [ ] Review from the native team if needed.
• [ ] No breaking change or entry added to the changelog.
• [ ] No breaking change for hybrid SDKs or communicated to hybrid SDKs.

[github-actions[bot]]

	Messages
:book:	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by :no_entry_sign: dangerJS against 84255ec861c114cf831bd5bbd48b103e924bd427

[codecov[bot]]

Codecov Report

:x: Patch coverage is 92.23301% with 8 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 84.972%. Comparing base (e61661b) to head (84255ec). :white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
Sources/Sentry/SentryClient.m	66.666%	4 Missing :warning:
Sources/Sentry/SentryDataCategoryMapper.m	33.333%	4 Missing :warning:

Additional details and impacted files

@@                        Coverage Diff                        @@
##           philprime/metrics-bootstrap     #6960       +/-   ##
=================================================================
+ Coverage                       84.928%   84.972%   +0.044%     
=================================================================
  Files                              458       461        +3     
  Lines                            27635     27730       +95     
  Branches                         12151     12188       +37     
=================================================================
+ Hits                             23470     23563       +93     
- Misses                            3907      4127      +220     
+ Partials                           258        40      -218     

Files with missing lines	Coverage Δ
SentryTestUtils/Sources/TestClient.swift	86.086% <100.000%> (+0.501%)	:arrow_up:
...ft/Integrations/Metrics/SentryMetricsBatcher.swift	100.000% <100.000%> (ø)
...ntegrations/Metrics/SentryMetricsIntegration.swift	100.000% <100.000%> (ø)
Sources/Swift/Protocol/SentryAttribute.swift	92.187% <ø> (ø)
Sources/Swift/Protocol/SentryMetric.swift	100.000% <100.000%> (ø)
Sources/Swift/Protocol/SentryMetricValue.swift	100.000% <100.000%> (ø)
Sources/Swift/SentryDependencyContainer.swift	98.319% <ø> (ø)
Sources/Swift/SentryExperimentalOptions.swift	75.000% <ø> (ø)
Sources/Swift/Tools/Batcher/BatcherScope.swift	100.000% <100.000%> (ø)
Sources/Sentry/SentryClient.m	98.185% <66.666%> (+0.758%)	:arrow_up:
... and 1 more

... and 36 files with indirect coverage changes

---

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[philprime]

@sentry review

[philprime]

@sentry review

[philprime]

@sentry review

[philprime]

@sentry review

[github-actions[bot]]

Performance metrics :rocket:

	Plain	With Sentry	Diff
Startup time	1190.73 ms	1211.46 ms	20.72 ms
Size	24.14 KiB	1.04 MiB	1.01 MiB

Baseline results on branch: philprime/metrics-bootstrap

Startup times

Revision	Plain	With Sentry	Diff
2d018e1e8f05f191199b7b1dc2f439ada894b7bc	1227.67 ms	1245.79 ms	18.12 ms
c17fb00bdea540635aba2a28b309d05906a33e00	1213.18 ms	1244.28 ms	31.10 ms
1fc93d0bdb3445096b15fd5db0cd74ec392a73d8	1231.06 ms	1261.37 ms	30.31 ms
b0e93524725794959be3ab81c4bf8fd9bb5d7fda	1229.50 ms	1265.81 ms	36.31 ms
40a71d5221e56bb78349ecc7ad52359a336c0d89	1221.24 ms	1263.70 ms	42.46 ms
9ee5daea9d275b72eaf3e546614d052b329046ad	1205.02 ms	1237.27 ms	32.25 ms
94a1efd66ca54b59247e16b561208f40f528a899	1212.39 ms	1250.19 ms	37.80 ms

App size

Revision	Plain	With Sentry	Diff
2d018e1e8f05f191199b7b1dc2f439ada894b7bc	24.14 KiB	1.03 MiB	1.01 MiB
c17fb00bdea540635aba2a28b309d05906a33e00	24.14 KiB	1.03 MiB	1.00 MiB
1fc93d0bdb3445096b15fd5db0cd74ec392a73d8	24.14 KiB	1.03 MiB	1.00 MiB
b0e93524725794959be3ab81c4bf8fd9bb5d7fda	24.14 KiB	1.03 MiB	1.01 MiB
40a71d5221e56bb78349ecc7ad52359a336c0d89	24.14 KiB	1.03 MiB	1.01 MiB
9ee5daea9d275b72eaf3e546614d052b329046ad	24.14 KiB	1.03 MiB	1.01 MiB
94a1efd66ca54b59247e16b561208f40f528a899	24.14 KiB	1.03 MiB	1.00 MiB

Previous results on branch: philprime/metrics-envelope

Startup times

Revision	Plain	With Sentry	Diff
63535b82c02e659862de227590d66775f51b534a	1228.64 ms	1255.27 ms	26.63 ms
34e473acf0c2231f4c7aecda08469c51f6b8054e	1195.53 ms	1222.53 ms	27.00 ms
f1ee7f4a4a468d79e01d7f9f3841307824f95636	1221.29 ms	1248.16 ms	26.87 ms

App size

Revision	Plain	With Sentry	Diff
63535b82c02e659862de227590d66775f51b534a	24.14 KiB	1.04 MiB	1.01 MiB
34e473acf0c2231f4c7aecda08469c51f6b8054e	24.14 KiB	1.04 MiB	1.01 MiB
f1ee7f4a4a468d79e01d7f9f3841307824f95636	24.14 KiB	1.04 MiB	1.01 MiB

[philprime]

@sentry review @cursor review