8282953: Drop MemoryLayout::map

[mcimadamore]

This patch removes the MemoryLayout::map method. This method was introduced to add some support for VLA (back when we had unbounded sequence layouts).

This method is quite limited when it comes to define transformations, as it can only alter one layout per call. As such, it is not useful to define global transformations to e.g. flip the endianness of all value layouts nested in a given layout.

We believe we can do much better than this (and have few ideas floating around) - but for the time being we'd like not to take the "good" name for a method that just doesn't seem all that useful.

When removing the method, I realized that the LayoutPath class had a lot of unneeded complexity:

• the size function is no longer needed, given that all layouts have a size
• keeping track of selected indices while navigating layout was only useful for the map operation, so I removed it
• we had two static methods addStride and addScaledOffset which did same thing; I dropped the first - the duplication was introduced when we dropped workarounds for "small" segments, in fact the leading MemorySegment parameter in the first method is now unused;
• I have greatly simplified the logic to create var handles from layouts; there is no need to do permutations (a similar simpler scheme was also used in the logic for computing offset method handles)

---

Progress

• Change must not contain extraneous whitespace
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Issue

• JDK-8282953: Drop MemoryLayout::map

Reviewers

• Paul Sandoz (@PaulSandoz - Committer) ⚠️ Review applies to b0d0f43

Reviewing

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[mlbridge]

Webrevs

• 02: Full - Incremental (c7296b37)
• 01: Full - Incremental (b0d0f439)
• 00: Full (38726900)

[openjdk]

@mcimadamore This change now passes all automated pre-integration checks.

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8282953: Drop MemoryLayout::map

Reviewed-by: psandoz

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[mcimadamore]

/integrate

[openjdk]

Going to push as commit f645d4f.

[openjdk]

@mcimadamore Pushed as commit f645d4f.

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