Performance improvements

From https://github.com/resteasy/Resteasy/pull/2479:

• Avoid unnecessary use of URI.create - rather do more lazily
• Multivalued maps will 99% of the time have 1 or maybe 2 entries for a key so don't allocate memory for 10
• Avoid unnecessary matcher creation when decoding when a string does not contain % in it - which is the more likely case for URI's to Rest resources

These changes increase throughput by about 2% on a simple Rest service and were found doing some hotspot analysis on load tests on Quarkus.