[docs] formatting and general pedantry

I'm not sure if the `distance-units` section is totally clear, when using the 'Geohash Cell Filter' and omitting a unit, the default is to interpret the integer as the 'length of the geohash prefix', not to default it to 'meter'. Maybe I'm being pedantic.

Closes #8744
Override write(byte[] b, int off, int len) in FilterOutputStream for better performance

Closes #8748
[TEST] guarantee REST tests execution order

REST tests are being shuffled before their execution. To guarantee their repeatability given the seed, their order needs to be always the same before the shuffling happens.

Closes #8745