Backport of repl: Display multi-line strings as heredocs into v0.14

[teamterraform]

Backport

This PR is auto-generated from #27045 to be assessed for backporting due to the inclusion of the label 0.14-backport.

The below text is copied from the body of the original PR.

---

The console and output formatter previously displayed multi-line strings with escaped newlines, e.g. "hello\nworld\n". While this is a valid way to write the HCL string, it is not as common or as readable as using the heredoc syntax, e.g.

<<EOF
hello
world
EOF

This commit adds heredoc detection and display to this formatter, including support for indented heredocs for nested multi-line strings. This change affects the apply, console, and output sub-commands.

Fixes #27039. Targeting an 0.14.0 backport because this is a fairly narrowly-scoped fix to a problem introduced by changes in the 0.14 release.

[codecov]

Codecov Report

Merging #27054 (56516bb) into v0.14 (af587cb) will increase coverage by 0.03%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
repl/format.go	99.05% <100.00%> (+0.29%)	⬆️
states/statefile/version4.go	58.19% <0.00%> (+0.23%)	⬆️
backend/remote/backend_common.go	52.70% <0.00%> (+0.72%)	⬆️
terraform/node_resource_apply_instance.go	75.79% <0.00%> (+0.79%)	⬆️
terraform/eval_diff.go	68.45% <0.00%> (+0.93%)	⬆️

[ghost]

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