Floss: Hcidoc: Refactor hcidoc parser to support other snoop types

Rename some variables to drop the LINUX_ prefix because it is uniform
throughout all btsnoop formats, not just the LINUX ones.
Refactor some classes to merge/split some logical responsibilities
to prepare for future implemented types.

Bug: 343594308
Test: m -j
Test: Test with the CLs in the chain
Flag: EXEMPT, floss only changes
Change-Id: I272f8f04a61e3e656b9a2261d691d52f445f130b