Split tracking related classes/functions into specific files

What does this MR do?

Related to #333220 (closed)

The current tracking logic is inside a huge file that hosts a too-specific class alongside helper global functions. This MRs separates the main class (Tracking) and the utilities/dependencies it uses in separate files.

No tests were changed as these are going to be addressed on #333224 (closed).

We now have files with a single responsibility (dispatch_snowplow_event, get_standard_context...), and a utils.js file. We'll try to have more consistency on #333226 (closed).

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
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• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.