Display all syntax error messages when catching SyntaxException

[barrettkingram]

Previously when catching syntax errors in the REPL, we were only showing
the last syntax error displayed by the ruby output. However, ruby can
generate multiple syntax error messages within a single SyntaxException.
For example, this code generates multiple syntax error messages:

$ ruby -e 'puts {"key"=>"val"}.to_json'
-e:1: syntax error, unexpected =>, expecting '}'
puts {"key"=>"val"}.to_json
-e:1: syntax error, unexpected '}', expecting end-of-input
puts {"key"=>"val"}.to_json

We can't predict which error message would be most helpful for the
consumer - we should show both of them.

This PR modifies the string replacement we're doing when printing
syntax exceptions so any number of syntax error lines will be shown
correctly.

Previous behavior:

[1] pry(main)> puts {"key"=>"val"}.to_json
SyntaxError: unexpected '}', expecting end-of-input
puts {"key"=>"val"}.to_json
                  ^
[1] pry(main)>

New behavior:

[1] pry(main)> puts {"key"=>"val"}.to_json
SyntaxError: unexpected =>, expecting '}'
puts {"key"=>"val"}.to_json
           ^~
SyntaxError: unexpected '}', expecting end-of-input
puts {"key"=>"val"}.to_json
                  ^
[1] pry(main)>

Issue: #2102
The error message of SyntaxError is different from Ruby's one

[kyrylo]

👍 good stuff