Expose telemetry log to extension API.

[efritz]

Add logTelemetryEvent command to the extension API so that extensions can send explicit anonymized events to the instance.

This will be used first by basic code intel to send events when a user receives precise or fuzzy code intel results. See sourcegraph/code-intel-extensions#193 for usage.

[codecov]

Codecov Report

Merging #7939 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #7939      +/-   ##
==========================================
- Coverage   40.73%   40.72%   -0.01%     
==========================================
  Files        1279     1279              
  Lines       66590    66595       +5     
  Branches     6320     6321       +1     
==========================================
  Hits        27123    27123              
- Misses      36991    36996       +5     
  Partials     2476     2476

Impacted Files	Coverage Δ
shared/src/commands/commands.ts	17.5% <0%> (-2.5%)	⬇️