Cleanup & improvements to perf-tester

[j-f1]

• clean up the code to remove unnecessary configuration options and other cruft from the original action
• quadruple the number of total benchmark runs, hopefully reducing the amount of noise regularly seen in benchmark runs
• remove false precision in the reported numbers
• tweak the automatic comment slightly

[github-actions]

Time Change: +942ms (10%) ⚠️

Total Time: 8,784ms

Test name	Duration	Change
Serialization/Swift Int to JavaScript	2,864ms	+516ms (18%)	⚠️
Serialization/Swift String to JavaScript	2,672.75ms	+291.5ms (10%)	⚠️

ℹ️ View Unchanged

Test name	Duration	Change
Serialization/Write JavaScript number directly	173.5ms	+2.25ms (1%)
Serialization/Write JavaScript string directly	176ms	-5.5ms (3%)
Object heap/Increment and decrement RC	2,897.75ms	+137.75ms (4%)

[github-actions]

Time Change: -164ms (1%)

Total Time: 15,566ms

Test name	Duration	Change
Serialization/Write JavaScript string directly	378ms	+22ms (5%)	🔍

View Unchanged

Test name	Duration	Change
Serialization/Write JavaScript number directly	334ms	-2ms (0%)
Serialization/Swift Int to JavaScript	4,987ms	-68ms (1%)
Serialization/Swift String to JavaScript	5,052ms	-122ms (2%)
Object heap/Increment and decrement RC	4,816ms	+6ms (0%)

[MaxDesiatov]

LGTM 👍