driver listCollections: fix, optimize and document legacy path
driver listCollections: fix, optimize and document legacy path

* how to use 'filter' in 2.x and 3.x mongodb
* /^[^$]*$/ vs /^((?!\$).)*$/ regexp >30% speedup:
* dead path and microoptimization

==== /^[^$]*$/ ====

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m1.772s
user    0m0.015s
sys     0m0.015s

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m1.744s
user    0m0.000s
sys     0m0.031s

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m1.751s
user    0m0.015s
sys     0m0.015s

=== /^((?!\$).)*$/ ===

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m2.440s
user    0m0.015s
sys     0m0.015s

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m2.202s
user    0m0.000s
sys     0m0.031s

olecom@U32U-RX007R_OLE /d/tmp/regexp
$ time node proc.js
432632

real    0m2.115s
user    0m0.000s
sys     0m0.030s

Signed-off-by: Oleg Verych <a5ce24b76737c0ca6b8faa55c4f938064a1695cf@gmail.com>

suprojs/supromongod,suprojs/supromongod,suprojs/supromongod