changesets: add changesets for all config changes

.changeset/five-games-grin.md

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+---
+'@backstage/cli': patch
+---
+
+Add `--lax` option to `config:print` and `config:check`, which causes all environment variables to be assumed to be set.

.changeset/happy-crabs-punch.md

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+---
+'@backstage/config-loader': patch
+---
+
+Added support for environment variable substitutions in string configuration values using a `${VAR}` placeholder. All environment variables much be available, or the entire expression will be evaluated to `undefined`. To escape a substitution, use `$${...}`, which will end up as `${...}`.
+
+For example:
+
+```yaml
+app:
+  baseUrl: https://${BASE_HOST}
+```

.changeset/lucky-guests-mate.md

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+---
+'@backstage/config-loader': minor
+---
+
+Removed support for the deprecated `$data` placeholder.

.changeset/tender-parrots-itch.md

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+---
+'@backstage/config-loader': minor
+---
+
+Enable further processing of configuration files included using the `$include` placeholder. Meaning that for example for example `$env` includes will be processed as usual in included files.