Restructure process branch: rename transition terms and update definitions

[XimeAixa]

Addresses points 8 and 9 (partial) of the review on OBOFoundry/OBOFoundry.github.io#2770.
Both reviewers flagged that transition (IDPO:0000080) is too broad as a label and the definition is protein-specific while the label is not.

• transition (IDPO:0000080) was deprecated due to semantic ambiguity and excessive generality.
• protein structural transition (IDPO:0000010) and higher-order assembly transition (IDPO:0000083) were placed as direct children of BFO:process.
• Process branch terms renamed to be self-explanatory.
• Process branch definitions transformed into Aristotelian form.
• has initial state (IDPO_0000088) and has final state (IDPO_0000087) range modified to BFO:process.