Cleanup docs directory and narrow CI skip patterns for retained docs files

[santoshpulluri]

Summary

This PR removes the legacy in-repo docs tree while intentionally preserving three useful docs files. It also updates CI workflow skip logic so docs-related skips apply only to the retained files, not a broad docs wildcard.

Why

The removed docs content is obsolete for this repository cleanup.
A broad docs wildcard in workflow skip rules no longer reflects repository reality after this cleanup.
Keeping only targeted skip paths avoids accidental CI behavior changes for non-retained docs paths.

What changed

Deleted most files under docs
Kept the following files:

• checklist-adding-config-fields.md
• add-a-changelog-entry.md.md
• fork-the-project.md

Updated workflow filters:

• go-tests.yml
• security-scan.yml
• reusable-conditional-skip.yml

Updated contributor docs references:

• CONTRIBUTING.md

[panman90]

LGTM

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>

[hc-github-team-consul-core]

📣 Hi @santoshpulluri! a backport is missing for this PR [23468] for versions [1.21] please perform the backport manually and add the following snippet to your backport PR description:

<details>
	<summary> Overview of commits </summary>
		- <<backport commit 1>>
		- <<backport commit 2>>
		...
</details>