DOC-9552: Add N1QL hint section

[simon-dew]

The following draft documentation is ready for review:

• Optimizer Hints
• Query Block Hints
• Keyspace Hints
• Select Syntax — added hint comment
• SELECT Clause — added hint comment
• USE Clause — added link to Optimizer Hints
• ANSI JOIN Hints — added link to Optimizer Hints
• Cost-Based Organizer — added Join Enumeration, link to Optimizer Hints

Docs issue: DOC-9552

[simon-dew]

• Remove EXPLAIN from example 8

[dhaggart]

• If it were me, I wouldn't separate '/*' and '+' (and '--' and '+') in the syntax diagrams - '/*+' and '--+' being clearer and less likely for someone to inadvertently insert whitespace before the plus.
• (Also the break-out for individual literal characters in the JSON syntax (text) for individual directives is confusing, e.g. '"' 'ordered' '"' ':' 'true', since JSON syntax would actually just be: "ordered":true.)

[miaobingjie]

Under "Optimizer Hints":

• I would agree with Donald here, having '/*' (or '--') and '+' separate implies there could be potential white space in between which is not true.
• Example 4: There is no comma after the keyspace name in INDEX hint, just a space

Under "Keyspace Hints":

• USE_NL - Simple Syntax: remove this sentence : "You may only use this hint once within the hint comment." you can have multiple USE_NL hints so you can either do USE_NL (a b c) or USE_NL(a) USE_NL(b) USE_NL(c)
• Example 3: the hint specified as USE_NL airline, should be USE_NL(airline)
• USE_HASH - Simple Syntax: remote this sentence: "You may only use this hint once within the hint comment."
• Example 4: this hint specified as USE_HASH ailine/PROBE, should be USE_HASH(airline/PROBE)