Refine query conditions

[eddelbuettel]

This PR extends support for query conditions to dense arrays (which requires queries of only attributes) and polishes one or two rough corners in doing so. A new example has been added, as has a test.

The example contains a sample query on an attribute in a dense array (which we write to memfs)

> tiledb_array(uri, return_as="data.frame", extended=FALSE,  
+                     query_condition=parse_query_condition(Temp > 90))[]
   Ozone Solar.R Wind Temp
1     NA     259 10.9   93
2     NA     250  9.2   92
3     97     267  6.3   92
4     97     272  5.7   92
5     NA     291 14.9   91
6     NA     222  8.6   92
7     76     203  9.7   97
8    118     225  2.3   94
9     84     237  6.3   96
10    85     188  6.3   94
11    96     167  6.9   91
12    78     197  5.1   92
13    73     183  2.8   93
14    91     189  4.6   93
> 
``` 

[shortcut-integration]

This pull request has been linked to Shortcut Story #19523: Refinements for QueryConditions.

[aaronwolen]

Looks good! I noted one possible typo.