[DOCS] A few grammar and word use corrections
log full exception in InternalClusterInfoService unless it's a ClusterBlockException
Add `getAsRatio` to Settings class, allow DiskThresholdDecider to take percentages

Adds new RatioValue class that parses ratios between 0-100% expressed in
either floating-point (0.13) or percentage (51.12%) notation.

Closes #5690
Update LongHash to work like BytesRefHash.

- rename "key" to "get"
- update and add more tests

Closes #5693