Docs: Fix typo in the javadoc for #tieBreaker()

Closes #8503
Snapshot/Restore: keep the last legacy checksums file at the end of restore

 This commit fixes the issue caused by restore process deleting all legacy checksum files at the end of restore process. Instead it keeps the latest version of the checksum intact. The issue manifests itself in losing checksum for all legacy files restored into post 1.3.0 cluster, which in turn causes unnecessary snapshotting of files that didn't change.

Fixes #8119
[TEST] Register data.path for all nodes on close in InternalTestCluster

We need to register those data paths otherwise we might miss path that
need to get cleaned when using local gatway etc. which can otherwise
cause imports of dangeling indices.

Conflicts:
	src/test/java/org/elasticsearch/test/InternalTestCluster.java
Docs: Update execution hint docs for Significant terms agg

copied over the relevant pieces from the terms agg

Closes #8532
Core: Added query/filter wrapper that builds the actual query to be executed on the last possible moment to aid with index aliases and percolator queries using `now` date expression.

Percolator queries and index alias filters are parsed once and reused as long as they exist on a node. If they contain time based range filters with a `now` expression then the alias filters and percolator queries are going to be incorrect from the moment these are constructed (depending on the date rounding).

 If a range filter or range query is constructed as part of adding a percolator query or a index alias filter then these get wrapped in special query or filter wrappers that defer the resolution of now at last possible moment as apposed during parse time. In the case of the range filter a special Resolvable Filter makes sure that `now` is resolved when the DocIdSet is pulled and in the case of the range query `now` is resolved at query rewrite time. Both occur at the time the range filter or query is used as apposed when the query or filter is constructed during parse time.

Closes #8474
Closes #8534