adding generic attributes interface

[varkey98]

Description

Adding a generic GetAll method for attributes so that all the attributes can be queried at once

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

Documentation

Make sure that you have documented corresponding changes in this repository or hypertrace docs repo if required.

[varkey98]

We would need to use fmt.Sprintf before passing the values to the filter, shall we just store the attributes as strings itself in that case? @ryanericson @tim-mwangi

[codecov]

Codecov Report

Merging #217 (d9abff1) into main (bf8e5c3) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
+ Coverage   58.81%   58.94%   +0.12%     
==========================================
  Files          55       55              
  Lines        2229     2236       +7     
==========================================
+ Hits         1311     1318       +7     
  Misses        859      859              
  Partials       59       59              

Files	Coverage Δ
instrumentation/opentelemetry/span.go	90.32% <100.00%> (+0.78%)	⬆️

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[tim-mwangi]

lgtm. @ryanericson please take a look as well since you were the original author for this :)