feat: replacing base plugin with instrumentation for xml-http-request

[obecny]

Which problem is this PR solving?

• Fixes Convert XMLHttpRequest plugin to instrumentation #1654

Short description of the changes

• Using Instrumentation instead of BasePlugin
• small changes to Instrumentation
• Updating WebTracerProvider to support old plugins and new instrumentation

[codecov]

Codecov Report

Merging #1659 (14bc751) into master (b703f9f) will decrease coverage by 0.00%.
The diff coverage is 96.15%.

@@            Coverage Diff             @@
##           master    #1659      +/-   ##
==========================================
- Coverage   91.36%   91.35%   -0.01%     
==========================================
  Files         165      165              
  Lines        5037     5043       +6     
  Branches     1039     1040       +1     
==========================================
+ Hits         4602     4607       +5     
- Misses        435      436       +1     

Impacted Files	Coverage Δ
...mentation-xml-http-request/src/enums/EventNames.ts	100.00% <ø> (ø)
...entelemetry-instrumentation/src/instrumentation.ts	63.63% <ø> (ø)
...strumentation/src/platform/node/instrumentation.ts	6.94% <ø> (ø)
...emetry-instrumentation-xml-http-request/src/xhr.ts	96.72% <95.23%> (ø)
...ackages/opentelemetry-web/src/WebTracerProvider.ts	100.00% <100.00%> (ø)

[mwear]

LGTM