feat: NodeUpdate needs only admin key to sign

[iwsimon]

Description:

Related issue(s):

Fixes #16493

Notes for reviewer:

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ -0.01% (target: -1.00%)	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (700e95e)	96496	62809	65.09%
Head commit (ec6b18a)	96496 (+0)	62800 (-9)	65.08% (-0.01%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#16495)	2	2	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.34%. Comparing base (700e95e) to head (ec6b18a).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #16495      +/-   ##
=============================================
- Coverage      63.35%   63.34%   -0.01%     
  Complexity     20100    20100              
=============================================
  Files           2527     2527              
  Lines          93677    93677              
  Branches        9804     9804              
=============================================
- Hits           59349    59344       -5     
- Misses         30730    30739       +9     
+ Partials        3598     3594       -4     

Files with missing lines	Coverage Δ
...e/addressbook/impl/handlers/NodeUpdateHandler.java	93.05% <100.00%> (ø)
...era/node/app/authorization/PrivilegesVerifier.java	89.15% <100.00%> (ø)
...m/hedera/node/config/data/ApiPermissionConfig.java	100.00% <ø> (ø)

... and 8 files with indirect coverage changes

[jsync-swirlds]

Lines 86-87 should also be updated to remove reference to the council creating the transaction and the "if node operator created", as the node operator will always create.

[jsync-swirlds]

Node account key is only required if that field is changing.
The admin_key is the signature that is always required.

Suggested change

	* for the account assigned as the current "node account".
	* assigned as the `admin_key`.