Add Transaction#set_context api

[sl0thentr0py]

• allow arbitrary contexts to be set on the transaction directly
• also including two other changes which are not changelog worthy
  • add internal Transaction#set_name api to set name on transaction directly
  • extract sentry-trace regex logic into Transaction.extract_sentry_trace helper for reusability

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.34%. Comparing base (3fad30c) to head (d8a3d5e).
⚠️ Report is 466 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #1947 +/- ##
==========================================
- Coverage 98.35% 98.34% -0.01% 
==========================================
Files 151 151 Lines 9414 9450 +36 ==========================================
+ Hits 9259 9294 +35 - Misses 155 156 +1 

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[st0012]

This also feel like an independent change to me so can base on master directly.
Can we add test case to clarify the precedence of Scope and Transaction's contexts, likely in sentry_spec.rb or hub_spec.rb?

[sl0thentr0py]

@st0012 regarding the based on master, I'll merge them in order so they'll each get their updated base as master.
I'll have to solve changelog merge conflicts every time otherwise.

[st0012]

IMO, all of these PRs deserve their own commits on master and independent changlog entries (not under the telemetry one) because 1) they're self-contained and 2) they also affect people who don't use sentry-opentelemetry.
I understand it's a bit tedious to resolve conflicts over and over, but it's worth doing to keep the history clear.

[sl0thentr0py]

I will move the changelog entries, but the history will be clear, I don't want to re-create all these branches.
If they get merged in order, the base will be master every time, they are just chained right now.

[st0012]

This seems to be mixed with other PRs' changes?

[sl0thentr0py]

@st0012 it needed a merge, done now