fix: clear user-facing typo families in docs + packages

[MukundaKatta]

Fixes #18427.

Picked up the unambiguous spelling typos listed in the audit (25 line changes across 14 files):

Contributor-facing docs/extend

• docs/extend/add-data-stream.md — Boostrap → Bootstrap
• docs/extend/add-mapping.md — aformentioned → aforementioned
• docs/extend/dashboard-guidelines.md — vizualizations → visualizations
• docs/extend/developer-workflow-import-beat.md — mutliple → multiple
• docs/extend/general-guidelines.md — quering → querying, chosing → choosing

identifer → identifier (5 occurrences): m365_defender × 2, tychon × 3

wether → whether (2 occurrences): sonicwall_firewall (fields.yml + README)

threshhold → threshold (12 occurrences): system package memory.{low,high,max} fields (fields.yml × 6, README × 6)

Left out the dev/testsreporter/github.go DRY-RUN> not run command item — that's a phrasing rewrite, not a clear typo, so better decided by maintainers.

Docs/description only; no schema, config, or logic changes. Fields' YAML keys and IDs are untouched — only the description: values.

[elastic-vault-github-plugin-prod]

Reviewers

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[elasticmachine]

Pinging @elastic/integration-experience (Team:Integration-Experience)

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[andrewkroh]

The modified packages each will need a patch version bump and an accompanying changelog entry. The elastic-package changelog add command can simplify making this change.