fix(browser-detector): fix name for user agent resource attribute

[david-luna]

Which problem is this PR solving?

Browser detector is sending the wrong semantic convetion for user agent. This PR adds @opentelemetry/semantic-conventions dependency into browser detector package and also aligns with other packages in the way incubating semconv are implemented.

Short description of the changes

• add semantic conventions package
• use ATTR_USER_AGENT_ORIGINAL attribute in resource detection
• add semconv.ts file with the incubating attributes and remove the current enum

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Unit tests

Checklist:

• Followed the style guidelines of this project
• Unit tests have been updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.95%. Comparing base (b3ca638) to head (1108b49).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6729   +/-   ##
=======================================
  Coverage   94.94%   94.95%           
=======================================
  Files         377      377           
  Lines       12730    12734    +4     
  Branches     2893     2893           
=======================================
+ Hits        12087    12091    +4     
  Misses        643      643           

Files with missing lines	Coverage Δ
...ntelemetry-browser-detector/src/BrowserDetector.ts	100.00% <100.00%> (ø)
...ages/opentelemetry-browser-detector/src/semconv.ts	100.00% <100.00%> (ø)

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