MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Adding request timeout
_ Fixing some tests
MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Fixing multipart test
MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Fixing encoding handling