fix for tgw peering multiple attachments issue

[rjjaegeraws]

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This changes fixes the CDK errors when trying to peer more than 1 TGW.

Original Error

rror: There is already a Construct with name 'Custom::TGWCreatePeeringAttachmentRole' in AccountStack [SharedNetworkPhase1CaWest_1]
    at Node.addChild (/app/node_modules/.pnpm/[email protected]/node_modules/constructs/src/construct.ts:428:13)
    at new Node (/app/node_modules/.pnpm/[email protected]/node_modules/constructs/src/construct.ts:71:17)
    at new Construct (/app/node_modules/.pnpm/[email protected]/node_modules/constructs/src/construct.ts:480:17)
    at new Resource (/app/node_modules/.pnpm/[email protected][email protected]/node_modules/aws-cdk-lib/core/lib/resource.js:1:1309)
    at new ImportedRole (/app/node_modules/.pnpm/[email protected][email protected]/node_modules/aws-cdk-lib/aws-iam/lib/private/imported-role.js:1:615)
    at Function.fromRoleArn (/app/node_modules/.pnpm/[email protected][email protected]/node_modules/aws-cdk-lib/aws-iam/lib/role.js:1:3167)
    at new TransitGatewayCreatePeeringAttachment (/app/src/lib/custom-resources/cdk-transit-gateway-create-peering/cdk/index.ts:48:26)
    at Object.createPeeringAttachment (/app/src/deployments/cdk/src/deployments/transit-gateway/peering.ts:86:47)
    at deploy (/app/src/deployments/cdk/src/apps/phase-1.ts:601:24)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)

[archikierstead]

LGTM