Add support for measurements at span level

[stefanosiano]

spans forward measurements to transaction

📜 Description

added measurements to spans
spans forward measurements to transaction
Example transaction

💡 Motivation and Context

Fixes #3180

💚 How did you test it?

Unit tests

📝 Checklist

• I reviewed the submitted code.
• 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.
• 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.

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

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

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Add support for measurements at span level ([#3219](https://github.com/getsentry/sentry-java/pull/3219))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against 32460b3

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	428.22 ms	538.29 ms	110.06 ms
Size	1.70 MiB	2.28 MiB	590.71 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
0810952	364.51 ms	468.08 ms	103.57 ms
2fad834	390.07 ms	470.80 ms	80.73 ms
2465853	422.61 ms	491.20 ms	68.58 ms
8ff8fd0	432.77 ms	495.18 ms	62.41 ms
2465853	400.64 ms	465.47 ms	64.83 ms
5e04ee8	365.26 ms	448.49 ms	83.23 ms
c554ca2	368.52 ms	430.74 ms	62.22 ms
4e29063	384.14 ms	447.74 ms	63.60 ms
0404ea3	394.73 ms	461.79 ms	67.06 ms
0404ea3	332.47 ms	401.12 ms	68.66 ms

App size

Revision	Plain	With Sentry	Diff
0810952	1.72 MiB	2.27 MiB	558.21 KiB
2fad834	1.72 MiB	2.29 MiB	577.53 KiB
2465853	1.70 MiB	2.27 MiB	583.82 KiB
8ff8fd0	1.72 MiB	2.27 MiB	558.15 KiB
2465853	1.70 MiB	2.27 MiB	583.82 KiB
5e04ee8	1.70 MiB	2.27 MiB	584.64 KiB
c554ca2	1.70 MiB	2.27 MiB	582.25 KiB
4e29063	1.72 MiB	2.29 MiB	578.38 KiB
0404ea3	1.72 MiB	2.29 MiB	577.52 KiB
0404ea3	1.72 MiB	2.29 MiB	577.52 KiB

Previous results on branch: feat/span-level-measurement

Startup times

Revision	Plain	With Sentry	Diff
ead0785	492.72 ms	628.02 ms	135.30 ms
268afc3	407.69 ms	470.34 ms	62.65 ms

App size

Revision	Plain	With Sentry	Diff
ead0785	1.70 MiB	2.28 MiB	587.99 KiB
268afc3	1.70 MiB	2.28 MiB	588.33 KiB

[markushi]

Nice one, l left a few comments mainly for discussion

[markushi]

LGTM!