Add FromAttributeIndices helper to pprofile

[dmathieu]

Description

Profiles attributes are stored in a single AttributeTable attribute, and then referenced in each substruct as AttributeIndices.

This means to read them as a pcommon.Map, a bit of pre-processing is required.
This adds an helper method so each component manipulating profiles doesn't have to reimplement it.

Benchmark:

go test -bench=BenchmarkFromAttributeIndices ./...
goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/collector/pdata/pprofile
cpu: Apple M1 Max
BenchmarkFromAttributeIndices-10         9789714               123.2 ns/op           140 B/op          4 allocs/op
PASS
ok      go.opentelemetry.io/collector/pdata/pprofile    1.952s
PASS
ok      go.opentelemetry.io/collector/pdata/pprofile/pprofileotlp       0.407s

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.85%. Comparing base (d977da4) to head (921f92f).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #12176   +/-   ##
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  Coverage   91.84%   91.85%           
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  Files         465      466    +1     
  Lines       25325    25334    +9     
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+ Hits        23261    23270    +9     
  Misses       1675     1675           
  Partials      389      389           

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The blocking request part is resolved.

[bogdandrutu]

This looks good to me in general, would like other to specify where this function should live.

Couple things:

1. Did you update benchmarks after latest changes?
2. We should document that changes to the return map are not reflected to the profile. Would like to understand how you think we should design the API that can do changes.

[dmathieu]

Did you update benchmarks after latest changes?

Sorry, they're updated now.

We should document that changes to the return map are not reflected to the profile. Would like to understand how you think we should design the API that can do changes.

I've added a mention that updates on the map will not change the record.
Making changes is a bit tricky, as we have to check the AttributeTable to find existing entries, possibly add new ones.
And we won't be able to remove data that's not used anymore, as we can't know it's not used by other records (that shouldn't matter much though).

We could have something like:

ToAttributeIndices(data pcommon.Map, table AttributeTable, record attributable)

That would properly update the AttributeTable with new entries, as well as the attributable indices.
That would be a full replace. So we could also have a single attribute add:

Addattribute(key, value string, table AttributeTable, record attributable)

[bogdandrutu]

PR looks good. But I want you to add an issue and mark it as blocker for stabilizing profiles to find a solution for updates and try it before stabilizing this package.

[bogdandrutu]

Sorry, they're updated now.

Numbers look much better than at the beginning 👯