Remove secure mint

[cll-gg]

This reverts the following commits:

0bc8c47 PLEX-1716 add observations wrapper with account context (#1520)
99c1fc5 DF-21815 Use seqNr as timestamp in the secure mint report (#1509)
75577eb DF-21546 Configure secure mint aggregator with data id (#1506)
4aeae90 Multichain Securemint Aggregator (#1484)
bcb59fd DF-21518 Remove seq nr validation in secure mint aggregator (#1470)
dabbeb9 DF-21518 Use a correct data ID in the sm aggregator (#1459)
5e5f10c DF-21518 Secure Mint aggregator: chainSelector passed in as string (#1452)
9d0a81a OEV-373 Add securemint plugin type and securemint aggregator (#1224)

Requires

Supports

[github-actions]

apidiff results - backwards-incompatible changes detected ❌

Module: github-com-smartcontractkit-chainlink-common

Status: ❌ 15 incompatible, 0 compatible

Incompatible Changes (15)

Element	Change
./pkg/capabilities/consensus/ocr3/datafeeds.AnswerOutputFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.DataIDOutputFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.NewSecureMintAggregator	removed
./pkg/capabilities/consensus/ocr3/datafeeds.ObsWithCtx	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SecureMintAggregator	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SecureMintAggregatorConfig	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SolanaEncoderKey	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SolAnswerOutputFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SolDataIDOutputFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.SolTimestampOutputFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.TopLevelAccountCtxHashFieldName	removed
./pkg/capabilities/consensus/ocr3/datafeeds.TopLevelPayloadListFieldName	removed
./pkg/capabilities/consensus/ocr3/ocr3cap.EncoderBorsh	removed
./pkg/types.SecureMint	removed
package github.com/smartcontractkit/chainlink-common/pkg/types/chains/solana	removed

(Full summary: https://github.com/smartcontractkit/chainlink-common/actions/runs/17651582622/#summary-50163763344)

[cll-gg]

We've decided to not remove secure mint functionality from chainlink-common, since it consists mainly of the secure mint aggregator, and this is used in the CRE smoke test securemint_test.
This test (introduced in this PR) validates whether the solana write target works as intended.
If we would remove the secure mint aggregator from chainlink-common, the solana write target would not be tested anymore.

Once there's another aggregator using solana, the secure mint aggregator can be removed.

cc @Unheilbar