Replace spacePattern in TextView word wrapping with strings.TrimRightFunc

[foxcpp]

Old code using regular expression does a lot of unnecessary work.

Benchmarks from #356 with significant difference

benchmark                                                                      old ns/op     new ns/op     delta
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      1890452       405316        -78.56%
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      2202032       432266        -80.37%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      2210060       434488        -80.34%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      2260540       447661        -80.20%

benchmark                                                                      old allocs     new allocs     delta
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      1712           659            -61.51%
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      1949           698            -64.19%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      1955           698            -64.30%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      1991           709            -64.39%

benchmark                                                                      old bytes     new bytes     delta
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      145969        23404         -83.97%
[...]
BenchmarkTextViewDraw/App=T/Color=F/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      170502        24437         -85.67%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=F/Scroll=T/Wrap=T/WordWrap=T-4      170905        24448         -85.69%
[...]
BenchmarkTextViewDraw/App=T/Color=T/Region=T/Scroll=T/Wrap=T/WordWrap=T-4      174575        24921         -85.72%

All benchmarks results