[RUMF-807] Broaden context types in APIs

[bcaudan]

Motivation

Using Context or ContextValue in our APIs is not convenient for typescript customers since customer interfaces won't be compatible with them due to index signature missing on interfaces.

Changes

Replace Context by object and ContextValue by any in APIs
Keep using Context and ContextValue internally.

fix #603

Testing

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I have gone over the contributing documentation.

[codecov-io]

Codecov Report

Merging #663 (f843141) into master (c645bf8) will increase coverage by 0.15%.
The diff coverage is 86.66%.

@@            Coverage Diff             @@
##           master     #663      +/-   ##
==========================================
+ Coverage   87.59%   87.75%   +0.15%     
==========================================
  Files          55       55              
  Lines        2531     2531              
  Branches      524      524              
==========================================
+ Hits         2217     2221       +4     
+ Misses        314      310       -4     

Impacted Files	Coverage Δ
packages/logs/src/boot/logs.entry.ts	100.00% <ø> (ø)
packages/rum/src/boot/rum.entry.ts	93.90% <50.00%> (ø)
packages/core/src/tools/contextManager.ts	100.00% <100.00%> (ø)
packages/logs/src/domain/logger.ts	95.23% <100.00%> (ø)
packages/rum/src/transport/batch.ts	78.94% <0.00%> (+10.52%)	⬆️

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