Fix metadata (se, email) stored in scope

[cstavitsky]

• We capture bits of data in the scope, later pulling it out to send it to the backend as headers. We also pull this data out in beforeSend and another place or two.
• This results in triggering performance issues for the demo
• During the v8 upgrade, we swapped out calls to set tags on the scope with, Sentry.setTag() (works on the isolation scope). That broke this functionality and performance issues stopped getting triggered with individual SEs' tags. this PR restores it

Tested locally

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 2.09%. Comparing base (a7b0b48) to head (e741605).

Files	Patch %	Lines
react/src/index.js	0.00%	7 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #542 +/- ## ========================================= - Coverage 2.09% 2.09% -0.01% ========================================= Files 37 37 Lines 812 813 +1 Branches 99 99 ========================================= Hits 17 17 - Misses 771 772 +1 Partials 24 24 ``` | [Flag](https://app.codecov.io/gh/sentry-demos/empower/pull/542/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | Coverage Δ | | *Carryforward flag | |---|---|---|---| | [api](https://app.codecov.io/gh/sentry-demos/empower/pull/542/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | `4.83% <ø> (ø)` | | Carriedforward from [a7b0b48](https://app.codecov.io/gh/sentry-demos/empower/commit/a7b0b48d4e7b944f72fc9f3ec53a829b10485ad6?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | | [frontend](https://app.codecov.io/gh/sentry-demos/empower/pull/542/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | `0.20% <0.00%> (-0.01%)` | :arrow_down: | | *This pull request uses carry forward flags. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) to find out more. | [Files](https://app.codecov.io/gh/sentry-demos/empower/pull/542?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | Coverage Δ | | |---|---|---| | [react/src/index.js](https://app.codecov.io/gh/sentry-demos/empower/pull/542?src=pr&el=tree&filepath=react%2Fsrc%2Findex.js&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos#diff-cmVhY3Qvc3JjL2luZGV4Lmpz) | `0.00% <0.00%> (ø)` | | | [Components](https://app.codecov.io/gh/sentry-demos/empower/pull/542/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | Coverage Δ | | |---|---|---| | [checkout_module](https://app.codecov.io/gh/sentry-demos/empower/pull/542/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | `4.83% <ø> (ø)` | | | [product_component](https://app.codecov.io/gh/sentry-demos/empower/pull/542/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sentry-demos) | `0.35% <ø> (ø)` | |