Improved seniority parsing for Vice President and Staff... positions

The seniority field in every job object in the Job Search endpoint can take one of these 5 values: c_level, staff, senior, mid_level, junior

Previously, seniority was not being correctly assigned for certain job titles:

• All “Vice President” roles were sometimes misclassified, being considered as mid-level roles, and all "VP" roles were considered C-Level.
• The “Staff” seniority label was applied too broadly, including roles like “Staff Nurse” or “Staff Physician” that do not represent Staff-level IC (Individual Contributor) positions.

With this update, seniority assignment has been improved:

• All “Vice President” roles are now consistently marked as Senior, rather than C-Level. While VP might sound like a C-Level title, in many organizations—especially banks and financial institutions—VP is a very common title that better aligns with Senior-level responsibility.
• The “Staff” seniority is now reserved only for explicit Staff-level IC roles, such as “Staff Engineer” or “Member of the Technical Staff.”
• Roles like “Staff Nurse” or “Staff Physician” are no longer misclassified as Staff; instead, they are mapped to more appropriate levels, often mid-level.