refactor(exporter-jaeger): migrate away from getEnv()

[pichlermarc]

Which problem is this PR solving?

Migrates away from getEnv() to the new functions and inline-defaults introduced in #5443. Since the Jaeger Exporter was only used in Node.js, everything stays as-is for the end-user. This is a pure refactor.

Refs #5217

Type of change

• refactor

How Has This Been Tested?

• Unit tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.91%. Comparing base (7438735) to head (8054d35).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5464   +/-   ##
=======================================
  Coverage   94.90%   94.91%           
=======================================
  Files         308      308           
  Lines        7971     7977    +6     
  Branches     1677     1682    +5     
=======================================
+ Hits         7565     7571    +6     
  Misses        406      406           

Files with missing lines	Coverage Δ
...ckages/opentelemetry-exporter-jaeger/src/jaeger.ts	95.40% <100.00%> (+0.34%)	⬆️