Ruby: Data-flow through hashes

[hvitved]

This PR is the culmination of a lot of preparatory work (#7750, #7677, #7914, #8641, #8786, #8870, #8898, #8938) required for precisely tracking data-flow through hashes in Ruby. The bulk of the work of this PR is about adding flow summaries (and tests) for the members of the Hash class. For some of the summaries, the method names overlap with existing summaries for the Array class, and for those we have adjusted existing summaries to account for hashes.

For example, the (simplified) original flow summary for the delete_if method was

// flow into first parameter of block
input = "Argument[self].Element[any]" and
output = "Argument[block].Parameter[0]"
or
// array indices may get shifted
input = "Argument[self].Element[any]" and
output = "Argument[self].Element[?]"

It has now been generalized to account for (a) for hashes, the value goes into the second parameter of the block, (b) only array indices may get shifted, all other known indices (such as symbols) will not:

// flow into last parameter of block
input = "Argument[self].Element[any]" and
output = "Argument[block].Parameter[" + lastBlockParam + "]" // lastBlockParam is bound via the call-site
or
// array indices may get shifted
input = "Argument[self].Element[0..]" and
output = "Argument[self].Element[?]"
or
// all other indices (including '?') do not get shifted
input = "Argument[self].WithoutElement[0..].WithElement[any]" and
output = "Argument[self]"

Note that if we are tracking a precise integer index (Element(0..)), then we assume that it will be an array, and hence conservatively convert the index to be unknown, although that wouldn't be the case if it was a known integer key in a hash.

[github-advanced-security]

Found 1 vulnerability.

[aibaars]

Looks good to me. Could you add some more QLdoc to the flow summaries?

[aibaars]

This looks great to me. A minor nit: I think it would be clearer to use more informative field names for the ConstantValues that represent an array index or hash key.

Is the slowdown in performance within expectations?

[hvitved]

Rebased to resolve merge conflict.