update hcl v2.10.1

[jbardin]

Update HCL to v2.10.1

v2.10.1 (July 21, 2021)

• dynblock: Decode unknown dynamic blocks in order to obtain any diagnostics even though the decoded value is not used (#476)
• hclsyntax: Calling functions is now more robust in the face of an incorrectly-implemented function which returns a function.ArgError whose argument index is out of range for the length of the arguments. Previously this would often lead to a panic, but now it'll return a less-precice error message instead. Functions that return out-of-bounds argument indices still ought to be fixed so that the resulting error diagnostics can be as precise as possible. (#472)
• hclsyntax: Ensure marks on unknown values are maintained when processing string templates. (#478)
• hcl: Improved error messages for various common error situtions in hcl.Index and hcl.GetAttr. These are part of the implementation of indexing and attribute lookup in the native syntax expression language too, so the new error messages will apply to problems using those operators. (#474)

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Fixes #29093
Fixes #29173

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