feat(observability): add bearer token, tls config and honor labels/timestamps to scrape config - #1833

Description

relates to #1832

First part of #1832: adds bearer_token, tls_config.insecure_skip_verify, honor_labels and honor_timestamps to stackit_observability_scrapeconfig (resource and data source).

Based on the review comments on #388 and on what the API returned in my tests (details in #1832):

• bearer_token is sensitive and ConflictsWith basic_auth — the API rejects both together (at most one of basicAuth or bearerToken must be configured). The description mentions that the API only accepts JWT-formatted tokens.
• honor_labels / honor_timestamps are optional + computed without a provider default; the API returns false when they are not set.
• tls_config is optional. If insecure_skip_verify = false is configured and the API leaves the TLS config out of its response, the configured value is kept in state, so there is no inconsistent result.

metrics_relabel_configs will follow in a separate PR, as described in #1832.

Testing

• Unit tests for the payloads (create and update), the mapping of the new fields and the TLS config mapping cases.
• TestAccResourceMin (observability) extended: the scrape config sets all four fields, checked on create, data source and update (update switches insecure_skip_verify to false, flips the honor flags and changes the token). Run against a STACKIT project: PASS.
• make fmt, make lint, make test, make generate-docs pass locally.

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Acceptance tests got implemented or updated (see e.g. here)
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)