readme badges and cleanup

[brettmc]

• adding badges to the various readme files to make more obvious the current versions
• list all packages and versions in main readme
• remove old README documentation (excluding development-specific), and direct users to opentelemetry.io
• link to opentelemetry.io where possible in package readme

[codecov]

Codecov Report

Merging #1053 (000c050) into main (49638ea) will not change coverage.
The diff coverage is n/a.

❗ Current head 000c050 differs from pull request most recent head 4d6e151. Consider uploading reports for the commit 4d6e151 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1053   +/-   ##
=========================================
  Coverage     82.03%   82.03%           
  Complexity     2175     2175           
=========================================
  Files           277      277           
  Lines          6185     6185           
=========================================
  Hits           5074     5074           
  Misses         1111     1111           

Flag	Coverage Δ
7.4	80.67% <ø> (ø)
8.0	81.97% <ø> (ø)
8.1	82.17% <ø> (ø)
8.2	82.17% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 49638ea...4d6e151. Read the comment docs.