Add Thread.each_caller_location

[jeremyevans]

This method takes a block and yields Thread::Backtrace::Location
objects to the block. It does not take arguments, and always
starts at the default frame that caller_locations would start at.

Implements [Feature #16663]

[headius]

I have done a quick implementation of this in jruby/jruby#7014.

It passes all tests except for the to_enum due to our Enumerator implementation always showing up in the stack. The caller_locations array and an array captured inside the enumerator do not match:

$ jruby -e 'def foo; Enumerator.new {|y| caller_locations.each {|l| y.yield l}}.to_a; end; pp foo'
["-e:1:in `to_a'", "-e:1:in `foo'", "-e:1:in `<main>'"]

$ jruby -e 'def foo; caller_locations; end; pp foo'
["-e:1:in `<main>'"]

This is filtering two elements in both cases: the caller_locations call and an each call.

The enum form makes it difficult to filter out the top N elements that are not relevant for caller since the actual trace capture then happens at a deeper level (under each at a minimum, but also under to_a). I am a bit confused why these elements do not show up in the CRuby version, since it seems to have a similar difference in stack:

$ rvm ruby-3.1 do ruby -e 'def foo; Enumerator.new {|y| caller_locations.each {|l| y.yield l}}.to_a; end; pp foo'
["-e:1:in `each'", "-e:1:in `each'", "-e:1:in `to_a'", "-e:1:in `foo'", "-e:1:in `<main>'"]

$ rvm ruby-3.1 do ruby -e 'def foo; caller_locations; end; pp foo'
["-e:1:in `<main>'"]